Well, I don't agree that the R-9 has a "quality control problem"...
Nonetheless, it's not that easy. Remington is not just taking over production of the R-9. Assuming they are going to make an R-9 (with some design tweaks), they are completing changing the production process--new location, new machines, new staff. Presumably they are also making changes to bring down the production costs. It's not exactly like making a totally new gun, but I imagine it is not a small undertaking either.
I would think that getting the R-51 problems worked out are a higher priority. The R-51 was a spectacular media failure that hasn't yet been fixed, while their connection to the R-9 is virtually unknown.