Just ran into this one today and I'm a bit stumped (haven't found anyone else in the forums that has had the below issue). In the above picture, this attack is set to roll a critical hit on a dice roll of 2 or higher (Not sure if this matters, but none of the dice rolls in the photo rolled a natural 20). The first roll is with advantage & the second is a normal roll--both work as intended. The last two rolls were done at disadvantage. As can be seen, the first of those rolled the same dice number on both sides, and the critical hit damage was rolled as intended. The last one did not roll the same dice number on both sides, and even though the lower number was still counted as a critical hit, the critical hit damage was not rolled. The value of the critical hit range did not seem to matter as the issue repeated regardless. Not sure why this is happening. I'm using the latest version of Firefox (the issue also happened in Chrome) & this is happening on the Roll20 5E character sheet v. 4.21 (The sheet is NOT set to NPC). I was also able to repeat this issue in different games using the same sheet.