What are these errors?

[Neša]

I had those errors show up here and on the test forum after upgrading to 2.1.6 after clearing they haven't been back.
Not sure if it was an upgrade task that kicked off once.

[lurkalot]

Not sure if it was an upgrade task that kicked off once.

@shawnb61

Explained it here. https://www.simplemachines.org/community/index.php?topic=591819.msg4191565#msg4191565