This is probably the issue... when you run a sta mode configuration on a single radio device, this connection must be established first before the wifi AP can come up. This is because the channel selection is dependent on the upstream AP.
With that in mind, you should set your radio configuration to use auto for the channel, and you should consider installing travelmate to help resolve issues if/when the upstream connection cannot be established.
Also, you didn't mention what device and OpenWrt version you're using:
ubus call system board