Yes, I have experienced this.
First time I refueled my HS phev np, pushed the button under the dash for 2 secs as book said, waited until the green notice came up saying refuel now, opened the cap and filled up, np.
Second time I filled up, followed the same steps but the cap wouldnt release. I tried and a couple of others at the service station did as well but it was stuck tight.
Rung up the dealer he said bring it out and wouldnt you know it he opened the flap twisted the cap and it came straight off and said whats the problem

Now I carry a small 8 inch shifting spanner in the glovebox and if its tight, put the on spanner gently on and with more leverage it comes straight off

I did notice there was a tight bit to get it moving for a start but once it moves, it comes off
Carry a small 8 inch shifting spanner in your glovebox and the extra leverage with that on the cap it comes straight off