Issues after last commit to src/MacVim/MMBackend.m

Describe the bug
I have several issues with the current master:

VIM - Vi IMproved 8.2 (2019 Dec 12, compiled May 30 2020 15:13:09)
macOS version
Included patches: 1-830

At startup, at least some of the highlight commands from gvimrc are not executed. For example, I have:

set cursorline
set cursorlineopt=screenline
hi CursorLine	NONE
hi CursorLine	gui=underline	guisp=gray

but do not get a underline. Furthermore I sometimes see artifacts of my status bar while scrolling.

I suspect the latest changes in src/MacVim/MMBackend.m as the reason for this behaviour. If I revert this part of the commit:

         while (CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, true)
                   == kCFRunLoopRunHandledSource)
              ;   // do nothing
+       [self processInputQueue];
  }
  - (void)flushQueue:(BOOL)force

I can no longer reproduce the issues and MacVIM behaves as before.

Can someone please check whether the [self processInputQueue]; is necessary at this point or whether it can cause such problems?

Environment (please complete the following information):

• VIM - Vi IMproved 8.2 (2019 Dec 12, compiled May 30 2020 15:13:09), Included patches: 1-830
• OS: macOS 10.15.5
• GUI: MacVIM

Start in src/MacVim/MMBackend.m and inspect the change that adds [self processInputQueue] after CFRunLoopRunInMode. Reproduce the startup highlighting and scrolling artifacts with the reported gvimrc settings on macOS, then compare behavior with that line reverted. Done means the regression is isolated and the appropriate behavior is covered by the project’s available verification process.