I sent the TS55R and CMS module back to Festool (their suggestion) and within a day they had looked at it and diagnosed a problem with the saw which made it impossible to fit the riving knife extension correctly and also (and unrelated) a warped sole plate (base) which caused the saw to cut at a slight angle to the dialled in setting. I understand that they are getting me a replacement unit. I reported the error in the cutting angle last July when I first bought the unit and they wanted to collect the saw and check it out but I felt I could live with the problem which seemed to be correctable by setting the angle to 0.5 degrees. I have been delighted with the saw despite this slight problem and look forward to any marginal improvement. I think the moral of the story is that if Festool offer/suggest to collect and investigate an issue, take them up on the offer.
I am very satisfied with the service I have received so far.
T15+3 set, CXS set, Centrotec set (2011), TS55REBQ, TS75EQ, 1400 rail, 1900 rail, 1400 LR32 rail, LR32 set, MFT/3, OF1400, OF1010, Guide rail adapter, edging plate, angle arm, chip catcher, small bore base, MFS400, MFS1000 profiles, RO90DX, RO150, ETS150/3, Domino DF500, Domino assortment systainer, CTL Midi, compact cleaning set, CMS GE, TS75 Module, OF Module, VL and VB extensions, LA Stopper, Sliding table, Carvex 420 Li 18 GG, core maker set, EHL65EQ, Syslite.