Drop down opening upwards (should open downwards)

I have a dropdown menu that was up and running and working as expected but suddenly without editing anything it started opening upwards rather than downwards.
I have another dropdown built in exactly the same way which is still working the way it should.
As all was good originally I can’t really figure out what’s happening here!

This gets even more fun. 2 instances of the same dropdown menu side by side, no difference between them, literally a copy paste. One opens up and one opens down… Please explain.

Please provide a link to the file so that anyone can take a look at your component settings.