Working for me on co-op now - turns out my friend somehow managed to install this mod incorrectly on two separate occasions (despite having installed WaW maps before). Everything is now working perfectly; didn't need to verify my game files or anything either.
I had a similar co-op error to the one above, with a mismatch for the Tokarev and also for the PaP version of the M1 Garand w/launcher (that I know of). I don't have plutonium installed (just T4M), and I've been trying to find a way around this but with no success so far. If I can find a fix, I'll post an update here saying what I did.
Other than that, I've got Der Riese installed and had a blast with it in single player. Best remastered map I've played by some margin.