Had an AOA vain failure on a 737-800 many years ago. Aircraft was in a cruise climb at around 6000 feet, A/P and AT engaged, when my PFD lit up with multiple warnings, low speed displays etc and we got the stick shaker. It’s was CAVOK, the * pitch and power settings were clearly normal * for the phase of flight we were in and the F/O’s instruments reflected this. Handed control to F/O, ran the checklists and told ATC we were coming back.
No real drama, but had it been a MAX with MCAS kicking in it may well have been more challenging ....