8devices habanero: mesh encryption problem

I'm trying to configure a mesh-net with 2 habanero-dvk. both with OpenWrt 21.02.1 r16325-88151b8303 / LuCI openwrt-21.02 branch git-21.295.67054-13df80d
Both with the same mesh configurations. Mesh 11bgn works. for mesh 11nac i cannot activate mesh encryption on one of the dvk. I can configure it, but the overview always shows Encryption: None (and no connection either).
after reboot same result. I tried wpad-mesh-wolfssl & openssl to get the same result.