Elevated SM will not connect to AP in 4.4.3, even when SM is upgraded to 4.4.3

I'm trying to upgrade our network to the latest firmware. I did a test on an AP with 20 clients. About half are elevated. I have 2 SMs that upgraded to 4.4.3 with little problem, except the GUI load time takes forever. But when I upgrade the AP to 4.4.3 from 3.5.6, they will not connect. When I downgrade the AP back to 3.5.6 they connect again. Its not interference, both antennas signal are -50. 

Any idea what would cause this?


If you run 40MHz and have XM devices please switch guard interval on the RF settings page to Long. Otherwise we need more details to figure this out. 



No, running at 10mhz. 

How much details do you need? We have all the same settings in both firmware versions. 

Ideally we need tech support dump from both AP and elevated device both running 4.5. It will be great if you can share it via the support case.