PostgreSQL 12 crash with segmentation violation

Hi,

I'm using posgreSQL for many years, all versions like 9x, 10x, 11x -
thank you very much for this excellent piece of software.

Now I have upgraded to postgresql 12 and get a crash about once per day,
unfortunately our midleware (Java via current JDBC) stops immediately on
this and all users are offline.

In  pg_log/postgresql-2019-10-31.csv I find entries like:

2019-10-31 07:03:03.750 CET,,,1516,,5db5cfa5.5ec,19,,2019-10-27 18:11:01
CET,,0,LOG,00000,"server process (PID 27439) was terminated by signal
11: Speicherzugriffsfehler","Failed proc
ess was running: update Location set enmea=$1, guid=$2, latDeci=$3,
lonDeci=$4, modifiedByLoginName=$5, poiObjectId=$6, timestamp=$7,
TRACK_ID=$8 where LOCATION_ID=$9",,,,,,,,""

I have built postgresql from source on a current Debian Linux with

./configure |--build=x86_64-linux-gnu|--host|=x86_64-linux-gnu
--||target||=x86_64-linux-gnu |--with-pam --with-openssl --with-libxml
–with-libxslt –with-llvm

Additionally postgis is compiled into and a little own c library
(language C strict) is used.

I have already disabled llvm withjit = off which didn't help.

How can I track down the problem?

thank you
Marcel