Generating citation keys silently fails after a few entries

[Linguista]

JabRef 5.2--2020-11-26--f1a2fa7
Linux 5.4.0-050400-generic amd64
Java 15.0.1

• [ x] Mandatory: I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

Citation key generation on a moderately large library (~1600 entries) fails after a small number of generated keys.

Steps to reproduce the behavior:

1. Select all entries in library.
2. Hit CTRL-G.
3. If bug Uncaught exceptions when genertaing citation keys (among other things) #7310 does not occur, then a small number of citation keys are generated (perhaps 5-15 out of 1600).
4. JabRef mistakenly reports no error, and can continue to be used.

Log File

Absolutely nothing is written to the log file when this occurs.

[github-actions]

This issue has been inactive for half a year. Since JabRef is constantly evolving this issue may not be relevant any longer and it will be closed in two weeks if no further activity occurs.

As part of an effort to ensure that the JabRef team is focusing on important and valid issues, we would like to ask if you could update the issue if it still persists. This could be in the following form:

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