I am getting the following error alert in a custom page whenever a run starts

json parser exception: SyntaxError: Unexpected token < in JSON at position 985, batch request: method: "db_get_values", params: [object Object], id: 1598691925697 method: "get_alarms", params: null, id: 1598691925697 method: "cm_msg_retrieve", params: [object Object], id: 1598691925697 method: "cm_msg_retrieve", params: [object Object], id: 1598691925697

Does anyone know why and what causes this? This does not affect anything and things seem to continue running fine.

thanks.