I've found I run into a stuck filament in my Sigma R16 with Capricorn tubing. It's mostly with the cheap spools I bought from Craigslist, which doesn't surprise me in the least. I may have solved the problem by adding a feed sponge to the path and putting a bit of PTFE liquid lubricant on the sponge. I was lucky to get one print completed between clogs in the tube before the modification. I'm on print job ten or more with the same filament and no clogged tubing.

I'm using 2.85 mm filament and it's a tight fit.