We had a similar issue: a class holding a variant could not be loaded from file when the file was saved on come computers using a built exe. The exe was built using LabVIEW 2018 SP1. We observed that files generated by those computers in built exes contain the version in the form 19.00.80.00 instead of the expected 18.00.80.00. At least on one of those computers that I could check, the runtime engine 2019 was installed so the problem could be fixed by un-checking Allow future versions of the LabVIEW Runtime to run this application in advanced category in build settings. This forced the exe to run in the 2018 runtime and generated the correct version. Most likely this was also the issue on your side.
Anyway, I decided to replace the variant in the class with other more basic data types.
Lucian
CLA
