when i edit a Blueprint in my project (.uasset) when i compile it work fine 0 problem but after when i save that .uasset a message popup and it says The asset failed to save when saving and i cant do anything
please help me i dont want to remake my game i have 2 week of hard work):
This is old, but for anyone who comes here looking for an answer, check task manager for other copies of the engine running in the background.
If you’ve had a crash and restarted, sometimes there is still a task running from an older version of your game. Once this is closed you’ll be able to save 
tyyyyyyyyyyyyyy
im having this problem but i dont have any extra processes running? any help
Thank you very much, I was going in circles and was starting to simmer.
Cheers
Still helpful in 2022. Thanks.
Well, that was obscure but super simple.
Worked. Thanks!
Still an issue out here, amazing that this hasn’t been resolved in 2022.
I had this problem, where the solution was that I had a blueprint that was referencing a macro I had deleted. Macros don’t always show up as problems in the compiler, especially if they are just missing.
In short, Blueprints might have missing references, which sometimes prevents saving.
and in 2023! Greetings from 5.1.1!
Thank you so much!
Still helpful in 5.5 - and 5 years later! How do I report a post for being awesome? 
Should be marked as the “accepted solution” if nothing else. Never would have even noticed that I had multiple projects running at once had it not been for this! Would have drove me crazy all day, lol.