You need to know that HDMI RAW is not the same thing as regular HDMI. HDMI video is a standard, and there is no reason I can see why the Ninja wouldn't record that off the R5C. But HDMI RAW means using the HDMI port as a data link to send computer data in some made-up format. This only works if both devices support the same HDMI RAW format. I can't find anything on the Ninja V's page which mentions the R5C's HDMI RAW format, so I don't know why you think this would work. OTOH, if you want to try it, make sure that the camera's "main rec format" is set to HDMI RAW, and the Ninja V is set to record it.
As for the R6, as far as I can see from the web site, it doesn't have RAW at all... so whatever you were doing there wasn't HDMI RAW.
(The Ninja can record in RAW -- IOW take whatever input it gets and convert it to ProRes RAW -- but that's completely separate.)
As for "shows all the screen settings on my footage" -- read the manual, particularly around page 149, "Superimposing Onscreen Displays on Video Outputs". Basically turn "OSD Output: HDMI" off. You may also have to set other assist features, like peaking, to be off on the HDMI.
