I have just tried recording this bass pattern on my Tyros4 and I also found that on playback with a CMaj chord, it played a C instead of a B!
Page 43 of the T4 Reference Manual says:
Rules when recording non-rhythm channels
• Use only the CM7 scale tones when recording the BASS and PHRASE
channels (i.e., C, D, E, G, A, and B).
As far as I was concerned, this was what I had done but the Bass pattern still played incorrectly!
I then checked the settings for the Bass channel in the 'PARAMETER' page of Style Creator, and the Source Root was correctly set at C and the Chord at Maj7.
The NTR was set at 'Root Transpose', and the NTT at 'Melody (Bass)'. I changed the NTT to 'Bypass' and exited Style Creator.
The bass pattern then played correctly, playing a B when triggered by a CMaj chord. I tried other chords (including minor ones) in different keys, and it seems to play correctly!
I can't tell you why this solved the problem, but it seems to have done so!
BTW you can return directly to the MAIN display from any other screen by pressing 'Direct Access' and then 'Exit'.
Regards
Ian