After a GeneXus upgrade you may have the following errors while generating GAM screens:
When you upgrade your GeneXus version, GeneXus also upgrades GAM so the GAM screens are imported again so they are modified (the screen itself and its code).
How to solve the issue?
In order to solve the errors, you need to change WorkWithPlus security to "None" as follows:
In this way, WorkWithPlus will import all the updated screens and you won't have the errors.
In order to avoid this kind of errors, you can disable GAM automatic update from Tools-->GeneXus Access Manager --> Installation Settings