A sub-idle stall while inflight can be caused by a rapid thrust lever movement towards idle. A sharp FE (if installed) will unload the engine(s) by opening bleeds. Sometimes that works. Normally, the engine must be shutdown with the fuel lever and restarted, which "resets" the fuel control (sometimes).
Slow thrust lever movement, particularly in the high-bypass engines is desired. A JT8 they are not.