Unexpected control subclass '2'

We had issues with our T1’s in our Asterisk server the other night. Rebooting Asterisk and Dadhdi did not fix things. I had to reboot the server, which is running Linux Redhat, to resolve the problem. When looking at the error logs I see a ton of the following error at the same time as our T1’s started having trouble:

WARNING[4840] channel.c: Unexpected control subclass ‘2’

Does anyone know what this error is?

AST_CONTROL_RING = 2, /*!< Local ring */