A global Jenkins Shared Library is configured. Caching for this library is enabled for 10min.

There are a lot of jobs in parallel running on Jenkins.
Sporadically and rarely the jobs fail with

10:39:23 Library my-jsl@rel-1 is cached. Copying from home.
10:39:23 ERROR: Library my-jsl expected to contain at least one of src or vars directories

My assumption is this is happening right when another job deletes the JSL. I could find another job that run at the same time:

10:39:22 Library my-jsl@rel-1 is due for a refresh after 10 minutes, clearing.
10:39:23 Caching library my-jsl@rel-1
10:39:23 Attempting to resolve rel-1 from remote references...

 Looking into the source code LibraryAdder.java  I'm wondering:
Is it really ensured the library is not deleted when currently being copied?
I understand it is ensured the library is not beeing cached when already beeing cached by another job, but if I understand the code correctly the library can be deleted even when it is beeing copied?