Hi Steven!
How did you managed to change the very last (forth) section of version number?
When you open Package.appxmanifest with project editor (Packaging tab), you can edit only the first three section, however you can overwrite the entire version number using the xml editor.
The related Microsoft documentation claims that last section of version number is reserved for Store use.
Modification of last section may not be recommended for sideloaded applications either. Leave 0 on the last section and use the first three sections for version control.
Maybe it helps.
"For Windows 10 (UWP) packages, the last (fourth) section of the version number is reserved for Store use and must be left as 0 when you build your package (although the Store may change the value in this section). The other sections must be set to an integer between 0 and 65535 (except for the first section, which cannot be 0)."
https://learn.microsoft.com/hu-hu/windows/uwp/publish/package-version-numbering
István