There might be a mismatch of firmwares in the mixers, but if you haven't succeeded to install a new firmware, PLEASE LEAVE IT THE WAY IT IS! The latest firmware version is not a good one for the AI mixers, not only because of the FireWire Display Lag, so leave your rack mixer on v9244 and your console on the appropriate version. There should be no problem using the latest UC versions, but generally 2.0 or 2.1 are known as being the best for AI mixers.
It seems that your SL 3242 AI has a problem. Check all connections and connectors and especially the option card. Try, if the mixer itself works, and then try to re-establish your AVB connection. It might also be that some settings have been changed on your rack mixer. If all that fails, contact PreSonus Support.