Error in the console

[Blackmadman]

In 99% of the server restarts I get one to three error messages that the plugin cannot find files. This is what the error messages look like:

[20:01:12 ERROR]: [Autorank] Can't find UUID storage file for n
[20:01:12 ERROR]: [Autorank] Can't find UUID storage file for s
[20:01:12 ERROR]: [Autorank] Can't find UUID storage file for m

It is not always the same letters, it varies every time. However, the files are present, even before the server restart.
The error occurs in MC 1.20.6 and also in 1.21. I use PaperMC, always the latest version, with both Minecraft versions.
And by the way: the plugin otherwise works great, even under 1.21.