Monitor vergisst Auflösung

I'm using a Macbook Pro (Late 2017) with a LG Ultra HD Display. The following problem occurs on a regular basis: When I connect the display via usb-c to my (closed) MacBook, the MacBook boots and the login screen is displayed. Sometimes, this happens with the correct resolution, sometimes it switches to HD resolution.

The funny thing is: when it has switched to HD resolution, the display settings in system settings doesn't look like this: .

Instead, there's a dropdown menu, which let's me select HD resolution or, alternatively, the highest resolution possible. But nothing in between.

There is a solution, albeit a very unsatisfying one: I have to unplug the usb-c cable a few times and then it might or might not switch back to the correct resolution. But it's not like: unplug, plugin and it's working. Usually, it's working after doing this between 2 to 7 times. It varies.

Any ideas?