The border for minimaps appears to be forced to show by MMBF. I use Sexymap to change my minimap to a square layout, while hiding the default border. When MMBF is on, it forces the border to always show despite this.

Reproduction:
Enable Sexymap, go to options - borders, check "Hide default border". Border is hidden as expected.
Enable MMBF - border now always shows
Disable MMBF - border is back to being hidden.

What version of SexyMap and Minimap Button Frame Redux are you using?

I can't replicate this with MBF-R 2.0.5 and SexyMap 10.0.2

For reference I'm fairly certain this has something to do with how they're being grabbed, I have not been able to track down how to remove the borders from gathered buttons so far.

If you're familiar, always feel free to submit pull requests.

Is this the same issue being described in #8 ?

If so, that actually gives me a starting place.

No, it's a different issue. The minimap border is the new border added in the Dragonflight UI. It looks like this:

when it should look like this

I've narrowed it down, oddly it seems to happen with these 4 addons enabled, but if any of them are disabled, then it behaves correctly:
MBF-R 2.0.5
Sexymap 10.0.5
Details DF.Wrath.10259.146
Outfitter (Equipment Manager - fan fixes) 10.0.0v5
However, it doesn't seem to happen on a newly created character, so it may be a profile issue.