X_T Conversion. I can open a X_T file, save it as a SW assembly, but if I close and reopen, it fails. I have tried a few attempts to save as IGES , STP, and ... files and repeating, but no luck. The assembly loads but with many errors and each component is suppressed and not retrievable
Make sure your part and assembly templates path are defined correctly under Tools > Options > Default Templates as there are chances that only assembly is getting saved but parts are not. And when you open assembly, there are not parts and hence the issue.
If that doesn't help fixing the issue, then please upload a X_T file