Sometimes one cannot always scroll down to see the full parent relations choices. They just don't fit.

One needs a few CTRL+--- to finally see all of them.
I agree, noticed same behavior many times, when working on public_transport or other route relations.
Ah yeah, this was #5280, which I fixed in c5ad8ad by adding a bunch of extra space to the bottom.
I guess it regressed..
@bhousel Thanks for the link. Turns out I made a CSS typo that nullified that style here.