the unity client doesn't allow to do any invalid moves (moving into an obstacle) so i'm not sure how that could have crashed your client.. it's possible, as with the QT, if the hunter was already moving and then the move became invalid later, because the path then goes through an obstacle, it becomes invalid, in which case it normally stops at the obstacle in the gamestate.
I don't know if it was unity or which client, but the sent transaction, had a waypoint set on a non walkable position and this shouldn't even be accepted in the blockchain i'd say, but maybe that check wasn't included and so went in. Anyway the game logic itself (huntercore) handle it, stopping the movement of the hunter on the last valid positionbut my client assumed (wrongly) that accepted moves were containing only valid waypoints and so my pathfinding+linearization alghoritm (i don't use the rpc call to compute the paths) crashed (of course I fixed that, but i was surprised by the invalid move itself)
Note that I talk about waypoints, so the cells that the user selected building their paths, because the game was already handling the eventual invalid moves that could happen during the linearization process.
P.S.
I'm not sure that invalid moves should be accepted into the blockchain, even if handled, because they violate the consensus rules (game rules). I'm wondering if there are other kind of invalid transactions that could cause bigger troubles