They need a rebuild due to the tips of the rotors having wear (its like the piston skirt). s'pose they probably have sorted them by nowadays tech but that might not be the case on an older unit like that. and with it being blown as well its likely to have seen some thrashing revs!
Ive got an old practical classics somewhere(of all mags) with a buyers guide to rotary engines i'l dig it out and post it on for you. sorry if i'm not much help though cos ive never worked on em in my line of work, just the usual 4-12pots