SBD message on RockBLOCK is no longer 48 bytes, but 54.

The status report message size increased beyond 50 bytes after the move to MAVLink 2 and HIGH_LATENCY2 message - it will consume twice as much credit as before.

That happened because the 2.5.0 version uses MAVLink 2 HIGH_LATENCY2 message for status reports and MAVLink 2 message headers are 4 bytes longer than MAVLink 1... 