Since the crash is reproducible on MariaDB 5.2.10, apparently it is not related to the upgrade, but either caused by a corrupted Aria log, or some tricky workflow which produced the unreadable log. Unfortunately, without the server logs it's hard to guess what kind of workflow it could be -- if the contents of Aria logs gives any hints, please let me know, and I'll try to generate something.
Since the crash is reproducible on MariaDB 5.2.10, apparently it is not related to the upgrade, but either caused by a corrupted Aria log, or some tricky workflow which produced the unreadable log. Unfortunately, without the server logs it's hard to guess what kind of workflow it could be -- if the contents of Aria logs gives any hints, please let me know, and I'll try to generate something.