Mercy has been the main attraction of bugs in Overwatch for some time with problems like the SR gain bug, and it is still happening in the new patch.
Mercy is one of the most important heroes in Overwatch, namely due to her ultimate, Resurrect, which is also the main reason why the Overwatch community hates her so much. There are currently two bugs in the game where it affects her ultimate, and not in a good way if it happens to your team.
The way that her ultimate works is that nearby allies who are dead will be brought back to life on the battlefield whenever she has her ultimate charged up and Q is pressed. However, the first bug that made Mercy's rez broken is that it will not bring everyone in the area back to life. Check out the clipped video below by the best Mercy player, EeveeA during his stream.
The second bug is actually worse than the first bug in my opinion. Whenever Mercy rez someone, that hero will come back to life on the spot where he was executed. However with this bug, instead of resurrecting a fallen comrade on the spot, it brings that teammate back to spawn after resurrected. This is a total waste of an ultimate as your teammate will have to run all the way back to the battlegrounds, which is exactly the same as waiting for respawn, not to mention Resurrect can easily change the outcome of any fight.
As you can see, these bugs has caused Mercy to be a burden to the team, so try avoiding playing her for the time being until Blizzard fixes this issue.