First of all, I'd like to again thank everyone who helped with the excellent diagnostics and troubleshooting tips. It is much appreciated.
A couple of things come to mind. First, you might get away with just breaking the edges on the barrel locking lugs and recesses. This would mean taking a sharp triangle file and putting a very slight 45° chamfer on the edges of the barrel locking lugs and using a scraper (a small triangle file with the teeth ground off to form a sharp edge) to put them on the edges of the lug recesses in the slide. These might only need to be a couple hundredths of an inch across. Just enough to spoil the catch of the edges you feel now.
This sounds a little scary. Are there any drawbacks to doing this? (You do just mean chamfer the lugs on the barrel, not the slide right?)
I know I do have a spare barrel link for a Sistema somewhere. If I can find it, I'll compare the Sistema and Star link with a micrometer.