Z axis issues? Slicer issues? File issues?

Hi all.

To start I have/use - Saturn 4 Ultra - Lychee Pro (runs out today) - MAIN - Chitubox Pro (runs out roday) - Does the slicing only - Settings/profile in the photos

So, I'm having a very odd issue. I am relatively new to resin printing, but have printed enough things to use up 4L of SUNLU Water washable resin, with most of that (90% at least) being successful prints and calibrations.

The only issues I've had thus far are with the build plate adhesion - had to lower the base exposure times to 14sec for small prints and up to 24sec for large prints or it is near impossible to remove from build plate, and the next issue was Lychee slicer crashes about...80% of the time when trying to slice anything with more than 500-1000 layers. But despite all that, I've managed to print plenty.

Now, my issue is mechanical (unless it isn't), I think. Basically, I have started using a nee resin so started another calibration print. However 3 times in a row they failed. Horribly (in photos). I watched the entire print on the 2nd attempt and what I saw was troubling. The Z axis, usually after the first 6 base layers, just...stops going up. So what happens is it just smooshes the print into the FEP over and over again. Then, oddly, seems to.switch to fast mode, smooshes the prints a bit more then randomly starts working properly again?!?

I have tried the following - level building plate - factory reset - change base layer exposure - tightened vat screws slightly - levelled the build plate...again - change bottom layer count and transition layer count - cleaned the vat and build plate - wirelessly update firmware - re-slice the file and send again

I have checked the following - z axis moves freely in manual mode - z axis cord not getting stuck/trapped - z axis works properly and stops where I feel it should when "Home" is pressed

Next steps for me to try - do a dry run with same file - dry run with different file - ask reddit for help (please) - ask elegoo support - cry...

I have used the exact calibration files at least 3 times with the water washable resin, so I feel it's not the file itself.

My question is, what is going on?! This only started when I swapped out resins to a new type 'SUNLU Standard 14k Solid Gray'. I feel it's not the resins fault though.

Please help me get back to being frustrated with layer shifts in dragon wings instead of being frustrated with whatever is happening now.