dovecot - Nov 2022 - Dovecot not offering TLSv1.2 after a few minutes

I have a very strange problem with one of our Dovecot servers (2.2.33.2) on
Ubuntu 18.04.

The current configuration allows for TLSv1 to TLSv1.3 connections. I can verify
those using testssl.sh, the tests will succeed (although correctly mentioning,
that TLSv1 and TLSv1.1 should be disabled). Running the tests again after about
5 minutes, the results are different. TLSv1.2 now shows "not offered and
downgraded to a weaker protocol".

Has anybody experienced a similar problem before?

Best regards
Markus
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> Has anybody experienced a similar problem before?
I have not, but testssl.sh might be buggy, try online service like 
internet.nl validator.

Zakaria.