To be fair I see this sometimes in svgs that are particularly complex. I havent been able to nail down the cause yet, but it appears that some part of my workflow inputs some sort of objects that overlap the others. I try to set a full or stroke on these “invisible” objects, and nothing happens.
It seems to happen when I pull the SVGs from sketchup more than any other situation. I keep meaning to try to duplicate it but just haven’t had the time.
The way I find them is to click on one path, select all that are the same color (which in these cases has meant “every path”), and then cut. Control-A after that should show anything that was left behind… and I see these weird select boxes with nothing in them.
I delete them and then do a paste in place (putting my paths back) and all seems right. It’s weird but then so is my workflow, I use a third party plugin for sketchup and it’s a little twitchy to say the least.
So, short version: have you looked for weird hidden objects in your imported svg bits?