Thanks for letting us know and including images of the error. We’re actively working to get this corrected and it appears that a bug in 2.12.0 causes some files to become corrupted upon saving. A fix for this will be released shortly but in the mean time, downgrading to 2.11.3 is the best option.
@poping2@reapermini We have a new PreForm release that will correct the error with saving. You can grab it here and thanks for reporting this - it’s always a big help in identifying bugs and getting them corrected quickly.