HI - using Moodle 3.0.2 on Linux
I've just run into the old error in quick grading where you enter the grades and save, only to see a message:
"The grades were not saved because someone has modified one or more records more recently than when you loaded the page."
Previous suggestions were to empty the caches, make sure 'no filter' is set, or to apply a patch (which refers only to an earlier version 2.4 I think). Reading the tracker shows this has been fixed in earlier versions, apparently...