Not sure if this is a duplicate of other reported rendering issues:

To reproduce, set laststatus=2 and define nnoremap <c-e> <c-e><c-e>. Then, open a buffer long enough and type CTRL-E repeatedly. You should see that part of the status line scrolls with the buffer.
Without Core Text the issue does not occur.
I can reproduce it with MacVim 8.1.950 (155) in macOS 10.14.3.
Thanks for reporting. Looks related to the scrolling performance improvement done in 155. Will need to take a look.
Do the changes in #858 fix this?
I have this, but not so hard as on your gif
@eirnym It鈥檇 also be helpful if you could test that PR!
@s4y I have no such issue with your renderer!
@s4y I have tried https://github.com/macvim-dev/macvim/pull/858 and I can confirm that it fixes this issue. Excellent!
I have just installed MacVim 8.1.1722 (157) and this is no longer an issue. Thanks a lot!
I'm afraid I have talked too soon. In fact, I am still having the same issue under the same circumstances. My MacVim version reads Custom Version 8.1.1722 (157) and it was installed with brew cask install macvim.
Could you please verify that you can still reproduce it, too?
@lifepillar it's happening, but in a slightly different way as it was.
Most helpful comment
Thanks for reporting. Looks related to the scrolling performance improvement done in 155. Will need to take a look.