Grub2 boot line indication out of sync on external monitor

[Karl Kastner]

The boot line indicator is out of sync on my external monitor connected via vga (Philips 241B6Q) with that displayed on my laptop (XMG/Clevo W230SS, nVidia GM107M). If I press the cursor down key, the indicator moves to the second line on my laptop screen, but not on the external monitor. If I press the cursor down key a second time, it moves on the laptop to the third line, and on the external monitor to the second line. The monitor thus displays the last but one state, so that the user frequently selects the wrong boot item. A screen shot is attached. This also happens in combination with other external monitors, so it is most likely a bug in the graphics system.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: grub2 (not installed)
ProcVersionSignature: Ubuntu 4.13.0-43.48-generic 4.13.16
Uname: Linux 4.13.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.3
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Aug 27 08:12:16 2018
InstallationDate: Installed on 2015-11-05 (1025 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
SourcePackage: grub2
UpgradeStatus: Upgraded to bionic on 2018-05-24 (94 days ago)

[Phillip Susi (psusi)]

That's really weird. I didn't even think grub showed up on a second monitor at all. What if you press C to go to the command line and type a few characters? As you type do they show up differently?

[Karl Kastner (kastner-karl)]

I press e and edit the boot command, then there is an instant reaction to the keyboard on all monitors, only the indicator in the main and sub-menu of grub seem to be affected.

I noticed that the sequence is at the moment slightly different then to what I originally described: cursor down one time -> indicator moves to the second line on the laptop but does not react on the external monitor, cursor down a second time -> indicator moves to the third line on laptop and on the external monitor as well. The indicator only lags when the cursor keys have been pressed an odd number of times.