I sometimes saw black borders around windows in ubuntu 14.04. It’s not only in r21.5 but also r21.6.
And it cannot be fixed unless I reboot system.
I found below bug report of ubuntu 14.04 was similar with this issue.
In this bug report, it said this bug has been fixed by updated Nvidia graphic driver.
My question is, is it possible for Nvidia apply the fix in L4T?