I recently ran into an issue where required fields that are initially hidden have their validation applied when both shown and a lookup rule is done in an unrelated field. This causes the highlighting in red and required message to appear before the user attempts to submit the form.
If the fields are not hidden, then this issue does not appear. It seems to be only the combination of showing the field and running a lookup rule done, both based on the same selection.
I am currently running Laserfiche Forms 12 and using the new designer, not the Classic.
I did see a similar question was asked previously but it was in 2015 and the only answer was about the fix being in an update.
Any insight is appreciated and I can supply more information if required.