2-UP Vertical window mode creeps wider with every click

[Pockitz]

I submitted this as a bug, but is there anyone else that has seen this problem before?

1. Using Indesign 18.2.1 on an M2 Macbook Pro with OS 13.
2. Open two documents and then select 2-UP vertical window mode
3. I expect both windows to stay the same width that I have set when opening 2-UP vertical window mode.
4. When using 2-UP vertical screen mode, the left hand window creeps wider by one pixel every time I click in the right hand window.