This is expected behavior. Basically, when you use the radio for both AP and STA mode, it is the STA mode connection (and really the upstream AP) that determines the channel selection of that radio. The AP mode instance must use the same channel as the STA mode connection. This is fine until the STA mode connection cannot be established (i.e. no ability to connect to the upstream AP), in which case the channel cannot be selected. If the channel isn't selected, the AP cannot start.
There are two general solutions for this:
- Use each radio as an AP xor STA. By setting up one and only one mode on the radio, there will never be a conflict.
- Use Travelmate which is designed for this exact situation and sets up a scenario where the system will attempt upstream connections, but gracefully fail when that is not possible and bring up the AP mode instead.