Yes-normal to get buildup. No-not normal for it to cause ftf's 150 rounds into a shooting session.
Not sure why you changed only the outer recoil spring, I always change both at the same time. Sounds like the gun isn't broken in yet, but I know you have a good number of rounds through it.
I would start looking into other culprits mentioned in other break-in and ftf threads such as the firing pin hole, breech face, etc. Small problems there may only manifest themselves as the gun gets dirty or the springs weaken.