maybl8 I know this is not supported but I see others have had success with this in the past.
Yeah, you may already know this, but the reason it's considered unsupported is because flash drives and SSDs use entirely different technology. Flash drives are designed with the expectation that you'll write something to them (e.g., an .ISO file), and then at some later time read that content and do something with it (e.g., install a distro). They're perfectly well suited to do that.
SSDs are designed to be replacements for hard disks, and as such are built to handle constant reads and writes. Yes, you can install a Solus editiion on a flash drive - I've done it, to satisfy my curiosity - but if you then spend any time trying to operate the OS from there, you're likely to burn up the flash drive pretty quickly.
I don't know what problem you're running into with that particular flash drive. I suspect it might have something to do with a write speed that the installer can't deal with. There all kinds of flash drives available, with all kinds of capabilities, but I suspect it's better just to give it up as a bad idea for now and move on.
If you let us know the reason why you want to do that, we might be able to come up with a better suggestion for trying Solus.