So just to clarify, you manually turned off all of the APRS “Ringer” functions in the APRS sub-menu section?
Is the radio doing anything or showing anything on the display when this happens?
How did you initially program the radio? By hand, RT Sys software, adms software, other (please don’t say you used Chirp)?
My only suggestion is to do a full reset and try manually programming in a few things and see if the problem returns.