Could be a bug, or could be this (from the fair play policy):
On his or her turn, each player has 15-20 seconds to make their first move. If this does not happen, the game will be automatically aborted. This has a negative effect on the Fair-Play record of the player failing to move. (But if you hit Abort, it affects your record! It's best to be patient for a few seconds.)
I'm just the messenger...
Many of my games are being auto-resigned. Has anyone seen this problem/glitch. I'm using the android version of chess. com on a Samsung 5.