A pendulum that keeps contradicting itself is almost never haunted. Four things cause it: a badly framed question, your own hand answering with your hope, a tool you never calibrated or cleared, or a real answer that is genuinely not fixed yet. Sort out which one, and the flip usually stops.

Why does my pendulum keep contradicting itself?
Because the pendulum is not a separate mind hanging off a string, it is a very sensitive amplifier of your own. Every clean answer and every maddening flip comes from the same source, tiny movements in your hand you do not consciously feel. Learn that, and contradiction stops being spooky and turns into something you can fix.
You can put a name and a date to this, if it steadies you to know you are not the first. Back in 1833 the French chemist Michel-Eugene Chevreul ran patient experiments on the swinging pendulum and traced the motion to involuntary muscle response, not spirits, the thing later writers called the ideomotor effect. I am not telling you that to tear the tool down. I am telling you because you cannot fix a flip you do not understand. The pendulum reads the part of you that already suspects the answer, and when two parts of you disagree, so does the string.
Is it the question, or the tool?
Nine times in ten, it is the question. A pendulum answers exactly what you ask, and most contradictions come from asking two things at once without noticing. Should I take the job is really three questions: is the money enough, will I be happier, is the timing right. Ask all three at once and the pendulum swings for one and against another and looks like it is lying to your face.
Break the question down. One idea, present tense, answerable by yes or no with no hidden second clause. Is this job right for me, this month, everything weighed, gets a cleaner swing than a vague dread dressed up as a question. If phrasing is new to you, the basics of asking a pendulum are worth a slow reread. Bad questions produce bad swings, every single time.
Are you moving it without knowing?
Yes, and so am I, and so is every honest dowser alive. That is the whole mechanism, not a flaw in yours. The trouble starts when what you hope for and what you fear pull your hand in opposite directions, and the pendulum, faithfully, wobbles right down the middle of them.
Here is how I catch my own hand at it. Ask it something you genuinely cannot know and have no stake in, the colour of the next car to pass, whether a coin in your closed fist landed heads. Watch how muddy the swing gets when your hope has nothing to grab. Then ask something you do know and do care about, and watch it snap clean. The gap between those two swings is your own investment moving the tool. The Victorian scientists who studied table-turning found the same thing, sitters shoving a heavy table across the room while swearing blind they were holding still. You are in good, faintly embarrassed company.

When is a flip actually a not yet answer?
Sometimes the pendulum wobbles because the answer honestly is not settled. A future that hangs on a choice another person has not made yet does not contain a fixed yes or no, so the string circles instead of committing. That is not a malfunction. It is the most truthful thing a pendulum can do.
Here is how I tell it apart from plain interference. A not yet answer is calm: the pendulum makes a slow, wide, undecided circle and holds it. Interference is jittery, it snaps yes then no then yes inside one breath. Calm ambiguity is a real answer, so wait and ask again in a week. A jittery contradiction means your hand or your question needs fixing first. If the same calm circle keeps coming back on something that truly matters, the honest move is to stop asking the string and choose a reading built for a yes or no decision, or to hold the question up with a live reader who can watch the swing alongside you.
Here is the boundary I will not blur. A pendulum has no business ruling on your safety, your medication, or a fear about your health, so if the question is really one of those, set the string down and ask a person who is qualified. A weight on a chain was never built to carry that, and it never will be.
How do I reset and recalibrate a pendulum?
When a pendulum has gone unreliable, treat it like a tool that drifted out of true and reset it on purpose. Hold it still over your palm and say, plainly, show me yes. Let it move on its own until a direction settles, then say show me no, then show me I do not know. You are not programming it, you are re-agreeing on the language between your hand and your eye.
If it stays scrambled, it wants clearing. Rinse the crystal under cool water, rest it overnight on salt or a windowsill in moonlight, and keep it off other people's hands, since a shared pendulum picks up everyone who touched it. Once it is clean and recalibrated, test it on three things you already know before you trust it with anything real. A pendulum chart or board can steady a wobbly tool too, by giving the swing fixed targets instead of open air. And if you would rather not rebuild a stubborn question alone, you can bring it to me and we will take it apart together.
When a pendulum is not your tool
If the string keeps circling on the one decision you most need settled, it may simply not be your instrument, and there is no shame in that. A short quiz can point you toward a method that suits your hands better, and the wider divination toolkit lays out what else is worth trying. Pick the tool that answers you cleanly, not the one you feel you ought to master.
Should I trust the first swing or the second?
The first, almost always. The first swing sits closest to your honest instinct, before your hope has time to lean on your hand. Second and third swings on the same question drift toward whatever you want to hear. If the first was genuinely unreadable, reword the question rather than asking the identical one over and over.
Does the direction of the circle mean anything?
It can, if you assign it. Many dowsers set a clockwise circle as yes and a counter-clockwise one as no during calibration, and treat any circle they did not program as the tool asking them to rephrase. A pendulum that only ever circles, never a clean line, usually means the question still holds two ideas at once. Decide the directions in advance so a circle is never a surprise.
Does my pendulum need to match my crystal type?
Less than the shops would like you to believe. A plain metal weight on a thread reads as well as a costly amethyst point, because the accuracy lives in your hand, not the stone. Pick something that hangs freely and feels honest to hold. If a certain crystal calms you and steadies your grip, use it for that steadiness, not for a power it supposedly holds alone.

A pendulum that flips is not broken and it is not haunted. It is holding up a mirror, and mirrors do not lie. They just show you a face that is still making up its mind.