This is sounding a bit like an issue myself and some others had with an Ignition upgrade: https://forum.inductiveautomation.com/t/8-1-35-upgrade-unable-to-extract-ignition-runtime-files-classes-jsa
I think it started with the 8.1.33 bump of the Java Runtime to version 17.
I suspect that the same issue that affected our upgrade is also affecting the clients. What I think happens is that when a client is run it fetches the resources from the gateway and extracts them - and like with the upgrade for some reason the classes.jsa file is immediately deleted.
I've just checked and on the same server we had the upgrade issue on I can't launch the designer
I hadn't noticed since we run the designer on our personal computers (which connect to our server).