Matek F-765 Not Detecting Failsafe

Running Arduplane 4.05 and then 4.06, the flight controller is not detecting a failsafe. When unplugging power to the receiver/unplugging the SBUS cable between receiver and FC/turning off the transmitter, the FC does nothing but command whatever mode it was in prior to the interruption. The receiver failsafe is set to command RTL mode, but this does not work (and shouldn’t be necessary). The only way I can get the FC to detect a failsafe is if throttle failsafe is set up, which while a good idea, hasn’t been necessary with the many other boards I’ve used. FS_LONG_ACTION and FS_SHORT_ACTION are set to 1. Any ideas? I’m guessing this may be a bug.