Your having issues with .689 bore with old paint. Likely that paint absorb a bit of moisture and grew in size.
Use fresh paint, i never experience any field paint in NY(cousins,hivi,PSI, and liberty) that had issues with .689. I used a stock Axe barrel and .685 dye CF. Never had an issue with ball breaks in the barrel with the .685
If i had any breaks is because the paint was weak from the start. I had a few field paint from liberty (gi sport field grade, probably 1 or 2 star equiv) The paintball shell was inconsistent. A few of them, had like a circle dot, about the size of a bolded period .
where it was only half a shell thickness. They actually broke in rotor rather, left a mess
But no barrel breaks.