Changes like highlighting made are not saved sometimes

Sometimes the changes I made in the pdf like highlighting and underline are not getting saved .

It happens with all files and not a single file & happens even when I am connected to WiFi.

It  says the "document" can't be saved to cloud as another "document(Recovered)" is saved 

what is Recovered document....?

How to avoid this?

is there any specific limit for storage in adobe cloud ?