Build plate un-leveling before 1%

[Raynx]

I've been using my Mars 2 Pro for a few months now and have just recently had this issue.

As the attachment shows the build head goes off balance usually before even 1% of the build is done. This happens after following the correct procedure for levelling the build plate, and the build plate is visibly level before entering the resin. 

So far I have tried:

• Setting the build plate screws tightly when leveling
  
• Setting the build plate screws only finger tight when leveling
  
• Checking that the printer is level (it is)
  
• Replacing the FEP (in case one side was sticking more than the other
  

But so far 6 different trials and retrials come to the same end - the build plate goes in the resin level, then comes out at or after 1% very much un-levelled. For what it is worth the screws holding the build plate have been tight or loose in different trials, but all to the same result.

Having trouble finding a solution so any help is appreciated