I've upgraded my BE800 to FQ v1.1.1 a while which don't have a problem.

However, when I check my BE800 & RE815XE today for any setting can be fine tuned, then I found MU-MIMO cannot be used.  If I'm not wrong, I used it when my BE800 was FW v1.0.12 & FW v1.0.9 (when I first installed to use it).  I've tried again to set to use "OFDMA+MU-MIMO" but it only set to "OFDMA only".  I tried to downgrade the firmware to v1.0.12 & v1.0.9 to verify if this is a bug by v1.1.1, but the downgrade process failed which should be due to v1.1.x can't be reverted to v1.0.x.

Any advise how I can use MU-MIMO on BE800 v1.1.1?  Please note I still can use OFDMA+MU-MIMO on RE815XE.  I'm use MESH.