Running 5.4.1 on Windows 10 Pro (2020). Edited, saved, exported and all well. Updated to 5.4.2. Tried to open the .bsdesign file and I get an error: "Can't Open Design. Oops, something went wrong." Only button choices are OK and Cancel. No helpful information. Same results with backup design file. Successfully opened the design file on another PC running 5.4.1 and it opens correctly.
This is pretty bad. Have you sent this via the bug report page? It seems to get priority.
Thanks. Will do.