This is working as designed for client/ap mode.

Basically it is working as a forwarder and if the client part fails to connect/authenticate to the remote ap then there is nothing to forward so the ap wireless is switched off.

If you want it to stay on all the time try configuring as client/ap(wds) instead. This means the local ap will set up to forward itself downstream using wds and therefore be abailable at all times with the client part picking up the remote ap if available.