TokuDB error -30995

Hi all,
We are using 5.5.40-tokudb-7.5.3-MariaDB-log MariaDB Server originally packaged by Tokutek but as Tokutek support is no more an option, apologies for posting here.
By checking MySQL error log there are infrequent error messages (once per few days) related to the same table with TokuDB engine.
151207 9:18:27 [ERROR] Got error -30995 when reading table ‘./dizzyhei1_seo/keyword_shortlist’
151207 9:18:27 [ERROR] mysqld: Deadlock found when trying to get lock; try restarting transaction

Check table returns OK, we didn’t noticed any other issues apart from the ERROR message inthe log, analyze table didn’t help.
Our database is quite busy one with 10k-20k QPS 20% writes. Usually I see [ERROR] mysqld: Deadlock found when trying to get lock; try restarting transaction
close in time to the error -30995, but I have multiple Deadlock errors during the day and only few or none -30995 errors.
Any ideas what this error -30995 means?
I can’t find any references on google.
Many thanks,
Igor