I have 4 different redfield scopes and they have been great. Not a single issue. One of em is at least 40 years old and been on a 12 gauge it’s whole career. Has kept zero for decades without being adjusted. It is great in low light. I almost feel it makes it brighter out . Just used it last night actually to harvest a late season doe. Sorry no help on where to rebuild it.
I have a Redfield that has lived on a 338win since the 80's. Glass isn't up to today's standards but it's good enough and the reticle seems to stay put.