Layer Shift issue?

[SolisInfotech]

Hi folks, I’ve completed a print, and its perfect. We then made some minor changes to some parts, and also hollowed out the model to save resin then re-printed. We experienced severe layer shift. NOTHING changed - same Form, same resin, same vat. - i don’t think the firmware changed. (dashboard doesn’t give that info, which would be a really useful feature). but i guess it might have done?

Form3
0.025
grey v4
print direct on build plate (as we always do)
31 degrees temp
plate seems solid with no play.

here is a pic of the original and the fail to show the issues

I’m doing another print how, and i’ve re-leveled the printer, greased the Z axis, re-seated the vat and am using a new vat.

Anyone got any ideas?

[Ciconiiformes]

Did you add an air-vent to the hollow structures?
And maybe you also have to add ribs and the likes to reinforce thin walls.

[SolisInfotech]

i understand the vents requirement - and no, they were unvented - but the layer issues are literally from the starting layers, so that’s not it.
We’ve re-printed on supports, and also re-levelled the printer and ensured the tray is firmly located too.
got a good print this time.