Found a bug…
4.2Dev
Crsf 6.10 and 6.13.
If somehow during flight rx loses power for a moment (bad solder or crimp) and the AP goes into RTL then if power is regained somehow AP keeps in RTL as the connection to the RX is not estabilished and the mode cannot be changed.
This happens with beta crsf 6.10 and 6.13.
Not on stable 4.11 crsf firmware.
Happened to me today, luckily plane loitered till battery died. At home did a lot of bench testing and the result was as described - short power loss of the rx causes AP to go into RTL and not reconnect to the rx when it regains power.