These are two different clients, then what you see is possible on NFS with client side caching. If you have multiple clients reading/writing to the same files you usually need to tune the caching options and/or use locking. I suspect that if you leave it for a while (until the cache expires) it will sort itself out.
In my test-case it is just one client, it missed a file deletion and nothing short of an unmount and remount fixes that. I have waited for 30 mins+. It does not seem to refresh or expire. I also see the opposite behavior - the bug shows up on 4.x up to at least 5.4. I do not see it on 5.10.
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