DrCeeVee

Hello @Dustin and everyone!
 
I finally found some time to do some more tests regarding this issue. It turns out that the problem was with the project files themselves, and NOT with Cura 5.3.1. For some odd reason, some of the parameters I had changed in Cura 4 were flagged as "not changed" in the project file, and Cura 5.3.1 simply didn't update them when the project file was loaded. I don't know what caused the project files to behave like this, perhaps a bug in an older version of Cura 4 I was using at the time.
 
I have now updated all my Cura project files, and they all load correctly in Cura 5.3.1.
 
In conclusion, there is no need to do anything in Cura 5.3.1. I have already closed the issue I raised about this in GitHub.
 
Many thanks to @MariMakes for taking the time to respond on GitHub, and please accept my apologies for raising an issue which was not what I initially thought it was... I'm happy that my confidence in Cura 5.3.1 has been restored and that my project files are now loading correctly.