And while we are at Boss GT history already, my next GT was a GT-10. And I still like the concept to this very day. Really easy on unit editing, quality hardware and, at least IMO - while not authentic - pretty decent amp sounds that are nicely dynamic.
Anyhow, also wanted to use it in 4CM. No idea what they did to the poor unit, but boy, that's a tone sucker if there ever was one. There must be something truly bad happening to your signal somewhere in the pre-amp portion of the thing - very likely straight at the input, because DI tracks recorded with it never sounded great, either. I could actually crosscheck by sending a decent DI take into it via USB...
Interestingly enough, whatever happens seems to be kinda compensated when using the internal amp, but connect any preamp in the FX loop and you'll be wondering whether it all of a sudden turned into a shitty preamp.
Yes, you could kinda compensate for the loss with some level and EQ tricks, so I've been running it along with a Laney LC50 (really nice amp IMO, gathering dust in the basement since 5+ years by now, poor fella...) for a while, but ultimately got pissed of so much that I abandonded the entire pre-amp section and only used the GT as a controller and FX unit, then went back to a rack with a loopswitcher instead.
And well, I actually used the GT on some gigs in 2024 (had to leave things on a truck for some weeks, so I didn't want to use something more valuable), just running it through an AMT Pangaea as an IR loader, and it held up amazingly well.