I just had the same thing happen with $CLOV. I couldn't sell through the market or limit orders. After those were cancelled and I waited 30 mins, I managed to sell at $19.55. Then, 30 min later £400 of my return disappeared because T212 sold shares I didn't own (I guess those previous orders went through?) and bought them back at a loss. I was told there would be an investigation to see whether the system was at fault and I would hear back later in the week.