Hi Karl,
Thanks for sending that over! I see two things that may be causing that mismatch error:
The first is the basic data rates being used between the 2.4 and 5 GHz radios. Your 2.4 GHz radios allow for legacy data rates to be used (1, 2, 5.5, and 11) whereas the 5 GHz radios don’t. To fix this, try disabling legacy data rates on the 2.4 GHz radios, or enable legacy data rates on the 5 GHz radios. Note that not all AP vendors will allow you to do this. If that’s the case, I would simply dismiss the dashboard notification.
The second thing I noticed is that one of your 2.4 GHz radios offers a higher max data rate compared to the other radios. I’ve noticed this happen when an AP is newer or has more antennas. For example, my 2nd generation Apple Airport Express has a max data rate of 144.4 Mbps for its 2.4 GHz radio, whereas my 4th generation Apple AirPort Extreme has max data rate of 216.7 Mbps. If I look at the MCS Index here, I see this is because the 4th gen model has 3 spatial streams which can offer higher data rates. Again, you might not be able to fix this with your AP config utility. You may need to replace the older AP models with the newer models so that they are all offering the same max data rate.
Please let me know if you have any other questions.