Head hit the print piece - again

So far, I’ve been unable to do long prints with my A350.
I’ve now used up 2 full reels of PLA making failed prints.
My latest one ran around 20 hours, and this is what I found this morning.
Pretty obviously the head hit the piece - HARD and slid the entire bed over.
This is the 2nd time this has happened on this print. (though it got farther this time.)

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Interesting. You can see that the magnetic bed slid. I wonder if the part is kind of warping and starting to pull the magnetic bed up off it’s contacts? Looks like we need some kind of clips that hold the corners in place so it can’t do this. Have you tried sliding the bed before you take the part off to see if it CAN slide easier? That might prove my point.

I know in my experience with the SM2 is that the part sticks to be bed very well and is sometimes quite hard to remove it.

The bed can slide, as you have to do that to get it positioned well.
I took the piece off and held it up against one of the beams.
The bottom of the part seems to be perfectly flat.

I tried again with a 1mm Z-Hop.
Still hit.

I think there are two kinds of Z-hop, one between layer changes and one between between rapid moves. Perhaps you can only do that in Cura or S3D. Which slicer are you using?

the only Z-hop I find in Cura is for Travel.

Following, sorry for the bad experience. Have you tried this?
Can we be sure that the layer shift is caused by slid heatbed?

I think you can be sure by looking at the picture posted above, the amount of magnetic place sliding is close to the amount of shift in the photo. It’s certainly possible that there was both bed shift AND stepper motor skip.If the part was struck by the print head, both could certainly occur.

I would say the real CAUSE is the fact that the part is warping and thus causing a head strike.

I’m pretty sure that the head hitting the piece due to warpage IS the issue that I’ve seen repeatedly.
On a long piece (like my 11"x4" ones), it only takes a tiny bit of warpage to make one corner of the piece high enough to hit.
I suspect, that in addition to just being a large piece, so just a little warp makes a difference, there may ALSO be an issue with the warp pulling on the magnetic bed until it releases suddenly, thus popping the piece up all at once so the head hits it.
If the piece released from the bed first - it’s likely that it would do so before the warp got as large, so the print would continue, just squishing the new layers a bit thinner.