[RAF.err] diags are always printed to Brightscript console (telnet 8085 for side-loaded app), intentionally - while they are non-fatal (they don't affect behavior, it is preserved exactly as before v2.5 when there were no such warnings printed), they relate detected issues, sometimes with recommendation to fix.
Regarding how ads are playing, use the tracking beacons (impression, completion, quartiles) stats if you have access to those. Alternatively you can use .setTrackingCallback() and i believe for that particular issue you would have received a call.