I built two runways. One of them had small stands for GA connected by taxiway. The other runway was meant for commercial (medium) only, but had GA (small) allowed.
GA-Flights were landing on the wrong runway and froze at the then end of the runway.
Simultaneously the starting GA-Flights froze just before the starting position of the correct runway.
After re-loading the savegame the planes started moving again - some starting from the runway they were next to, but two planes also crossed the grass (taxiing) between the runways which do not have any connection.
See savegame and screenshot attached.