It sounds as you’ve set an auto program..
The Residual Drying Automatic sensor is designed to cut-out after a few minutes.
(It monitors resistance of metal paddles to outer drum, hence if no damp clothes are in drum it detects high resistance & shuts off)
If you want to check drying in manual mode set it to “timed only” drying program!
Send me your e-mail address in PM if you need anything further.