MariaDB fails to start after update: Assertion failure in file pars0pars.cc line 818

After upgrading from MariaDB 10.1.32 to MariaDB 10.3.9 on one production server (several others did not encounter this problem), the server failed to start with the following problem:

2018-09-26 01:40:31 0x7f1a0dc088c0 InnoDB: Assertion failure in file /home/buildbot/buildbot/padding_for_CPACK_RPM_BUILD_SOURCE_DIRS_PREFIX/mariadb-10.3.9/storage/innobase/pars/pars0pars.cc line 818
InnoDB: Failing assertion: sym_node->table != NULL

We managed to start MariaDB by using "innodb_force_recovery = 3" and move all data to other database servers. However a drop database command causes the same issue to appear, even with the recovery on 3.

A "mysqlcheck --all-databases" did not find any issues and a mysqldump of all databases also did not cause any problems. This is the reason we think this might be a bug and not just data corruption.

Enclosed are 2 problem traces. The MariaDB-pars0pars.cc-818-first.txt contains the problem just after starting the server in 3.1.9. The second contains the problem with innodb_force_recovery = 3 after a database drop was executed. It failed a few times after the database drop and then started again correctly.