Connectors vanish in certain positions

Summary:

When connected objects overlap, there are some angles where their connectors are not visible (also don't seem to be below the objects, as far as I could see).

Steps to reproduce:

Video (unnecessary long):

Peek_2021-05-17_16-43

What happened?

Connectors aren't always rendered.

What should have happened?

Connectors should always be rendered.

Note: the Connectors feature is supposed to be refactored into an LPE. It would still be nice if this case were tested with the upcoming LPE, too.

Version Info:

- Inkscape Version: 1.1rc
- Operating System: Linux Mint 20.1