OP, I had a partially similar experience with one of my 5-25 s&b scopes. After buying scope new, using it for a couple years on a prs gun, I noticed tiny specks of whatever start appearing on the reticle. I took pictures when I first noticed it, then again after it got noticeably worse. Emailed and spoke to CS about it. I paid $60ish to ship scope back for repair. Tracking indicated they received the scope on a tues. Two weeks later I called to get an update on progress. I got pretty much same explanation, they had used a grease from another company and that had started to degrade or breakdown causing the specks to appear. Totally understand, shit happens. They repaired it, did an inspection on the rest of the scope and verified all was good. About 10 days later (total time they had the scope was 23 days) I received a shipping notification saying it was on its way back to me.
After recieving scope, I inspected it thoroughly for any issues. Found one. Same issue with parallax being gritty, which I never had before. Called CS and they sent an overnight shipping label to return the scope. Boxed up and out next day. Scope was again delivered to them, and within 48 hours of delivery I received notification saying they shipped it back overnight. I received the scope next day, and again inspected it. Everything was right this time, no specks, no gritty knobs, no issues. About 4 months go by before I pulled that rifle out.
We were going on a trip to Utah and had that scope on one of my rifles that went through checked baggage. Upon arrival in SLC, while in my hotel room, I noticed there were again visible particles inside the scope. I was pissed to say the least. So I contacted CS for the third time. Provided pics of the new particles I had seen, and was promptly given another overnight shipping label, but since I was on the road and out of state I had it sent to the place we were going to be staying, an Airbnb. I was lucky enough to borrow a scope from my buddy, shout out to #DirtyDerek, for a few days until I received mine back. Instead of getting my original scope back, I received a nib warranty replacement. Which was totally fine with me. To be honest, I wouldn’t have the confidence in my original scope like I did before all this mess started. So in closing, every company that makes a product, no matter the cost or QC process, inevitably produces a lemon every once in a while. It’s just how do they make it right with the customer. Imo S&B did right by me, and I am grateful to have a scope I can trust again. Did I pay for that confidence, sure, but I received a product that I feel is comparable to the amount of money I shelled out.
Piece of mind and not having to question your gear is why I don’t shoot a rem700 with an IOR optic.
I shoot AI and Schmidt & Spender.