Two prices exist at once on a derivatives venue and they are used for different things.
Last price is what just traded on that venue. It is what the chart draws and what your fill happens at.
Mark price is the venue’s estimate of fair value, typically built from an index of several spot exchanges plus a funding-based adjustment. It is what your unrealised P&L and your margin are calculated from, and therefore what decides whether you are liquidated.
Why venues do this
Because valuing positions at the last trade on a single venue is trivially manipulable. Push a thin book far enough for one print and, if that print governed margin, you could trigger liquidations across the entire venue — then buy what the liquidation engine has to sell.
Marking against an index of external spot venues removes the incentive. Moving one book no longer moves everyone’s margin, because the mark barely notices a print that the rest of the market disagrees with.
The consequence you feel
A wick on the chart that appears to reach your liquidation price may not have liquidated you, because the mark never got there. The reverse also happens: you can be liquidated at a level the visible chart never printed.
Both look like errors and neither is. The chart is showing last price and the engine is reading the mark, and on a violent move in a thin book those two can differ meaningfully — which is exactly when it matters most, and exactly the condition described in liquidation cascades.
What to do about it
Set stops with the knowledge that your own exit executes on last price while your liquidation is judged on the mark. And treat the gap between them as a liquidity read in itself: a venue whose last price departs from a multi-exchange index is telling you its book is thin right now, which is the same signal in a different form as the divergence discussed in where the price is actually made.