Every now and then the craft will become uncontrollable while in map mode. The "SAS" indicator becomes somewhat greyed out and the keyboard controls stop responding. Switching map mode off and back on and then toggling the navball back on restores the control, so it is not a matter of lacking a pilot, electricity, comms connection, time warp or anything like that.
I get a feeling it usually happens after editing maneuver nodes, but not always and the relationship with that is still not clear to me. Just now it happened after I made a node and burned its required burn, just as I pressed the final "x" to end the burn. If it had happened a second sooner it could have been disastrous.