I also get this frequently,.Sometimes saving the project fixes it but other times especially when nested in blueprint camera post process settings, I have to do a restart.
It’s whenever I edit the Global Color Grading options. After I do that, I hit play, and then it pulls up an error from the side saying: “Can’t Play in Editor while performing Edit X Operation”, and it won’t allow me to preview the game. I’m making an advanced first person shooter named SPECTRE, and it probably doesn’t have an effect on anything, but I said it. Anyways, what I’m saying is: This Edit X Operation thing confuses me, and it needs to be fixed. I know it’s hard, but I don’t want to make a small change in the editor, and then have to restart it every single time.
- Zach of ZCProductions
If someone can give an answer to this, I’ll be happy not having to restart it every time.
Sounds strange. Can you tell us what setting exactly and where you adjust it? Is there a message window (usually bottom right)? For things like that we need a reproducable case =)
*Also check your Output Log for Clues
Have the same problem, so I’m assuming this is a bug.
It happens when clicking on a value slider in the Post Process Volume, when the value is highlighted blue and you’re given the option to type in another value, and only once you do type something in will this occur.
Seems the fastest way you can stop this bug is by dragging the value slider side to side after it gives you the error, then it should go away. You don’t have to change the value, just move it slightly and back to the position it was at and it should go away. Or just drag the slider in the first place and don’t do manual type ins to avoid this bug entirely.
You have to save your level after changing a post process value 
And then wait until your gigantic level takes a minute to save? It’s faster to just move a slider.
Become a buddhist and you will be happy
I had a very similar issue and re-opening the Level worked for me.
Just save level