When I decided to start my project fresh, I downloaded AdvancedHMI V398s. Opened it, Built it, started my project (for AB SLC 5/04 using DF1).
I reconstructed the main screen, with 2 Form Change buttons (but not assigned to a from yet) then added 2 forms, reconstructed the 2 forms as normal, then when I wanted to assign which form to open to the Change Form buttons, I did a Rebuild. & got a lot of errors in MfgControl.AdvancedHMI.Controls & .Drivers - when I went to the Debug folder in Explorer there were no such files.
I copied the file from the V398g folder to V398s, reopened VS & tried to rebuild again, but got 60 errors: (doesn't seem to be compatible versions)
After the errors I tried to reopen all 3 pages & got VS errors, had to click Ignore & Continue, but then got 3 empty screens, all reverted to default size 300x300, no background color, no objects at all.