Loud Grinding with Z hits 0

[manifest3dg]

I just got my Elegoo Saturn yesterday and printed the test rooks and went to bed. The next morning with I woke up the build plate was all the way up and nothing stuck to it. Nothing seemed to print, nothing on the plate or in the vat. This afternoon I went to start a second print and when the build plate lowers to print, it gets stuck there and makes a grinding noise. I stopped it, used the manual features to move the plate up and down the Z Axis and that works fine, but when I press to lower the Z Axis to zero it does the same thing, like the endstop isn't recognizing it's at zero and it's trying to keep going. I updated the firmware to no effect. Any idea why this is happening or how to fix it?   PS: This is my first resin printer.

[url=https://www.reddit.com/r/ElegooMars/comments/dcty93/grinding_when_z_axis_gets_to_zero/][/url]

[manifest3dg]

Just got my Saturn going again.   I unplugged the power for 1hr, reset to zero and still the same.   Unplugged power over night, removed, cleaned and re-zero build plate.   Removed VAT, drained and cleaned VAT.   This is where I found my issue...while cleaning out the VAT I found 2 round discs from the rooks that failed to stick to build plate!   Those 2 discs where preventing the build plate from reaching zero.   Hope this helps.

happy printing

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P.S.
Though I might share my rookie mistake.   When cleaning out the vat I put the VAT and build plate on a plastic meal tray and sat the tray outside for a few mins while I cleaned the cover and base unit.   When I returned to start cleaning the VAT and build plate that little bit of UV light had already started to cure the resin in the VAT and the build plate.   Normal 99% ISO was not cutting it...had to bust out the acetone.   Lesson learned