Ticked created after discussion with Alex.
Detected on LI-5.0.0.328, server mode = Super.
Server process does not keep opened any .fdb file but execution hangs.

FB dump, stack trace and snapshot were stored in:

https://drive.google.com/drive/folders/1ygATSATHs64Aw9CenXvEIV_5tGBrla4u?usp=sharing

Stack trace is also in attached zip here.
gdb-firebird-hanged-on-core_4337.fbt.txt.zip