I have a single user (as far as I know) experiencing some sort of layering or positioning issue in my production app. He sent me this screen shot:

The same screen looks fine for me:

and here it is prior to clicking on the calendar:

The above example is a gallery, but the issue is present in other areas of the app, too. For example, here is a label that is not within a gallery.

Positioning in both examples is being handled relative to other items on the screen: ie - Label2 Y position is set to Label1.Y+Label1.Height.
The user is on a Macbook with Chrome Version 88.0.4324.150 (Official Build) (x86_64) and Javascript V1.7. He states that the issue is consistent within Chrome, but does not appear when using Safari. I have tested on my end with the same hardware and Chrome build, however, and have not been able to recreate the issue. Everything looks perfect for me as well as other users (as far as I know). Any idea what might be going on here?
Update with more context:
This appears to be related to the user's monitor resolution. He is on a 3440 x 1440 display. It works fine if the app is launched on the built in Macbook display, but not on the external monitor. Also, the problem seems to to be specific to controls that are within Containers, and not others.