So I've used OpenWrt on three different devices and seen the same issue on all of them.
I can run WISP mode on a 2.4Ghz radio - simultaneously running Client and Master connections.
But no dice on a 5Ghz radio - always the 5Ghz is happy to run either as a Client or a Master connection, but never as both simultaneously.
Is this expected or unusual.
Routers tested
Archer a6 v2 and v3, Archer a7 v4.
OpenWrt 22.03.5 and OpenWrt 22.03.3