Cool, when I'm in my parental home where the Philicorda lives, I'll give it a try! In fact, al lot of keys were also broken, so sounded like another note, really bad. For the rest, I tried to make as many individual samples as I could and interpolated the really bad tones (and found then out that the nord sample editor does this for you automatically...). Considering the size of the samples, you also sampled each note individually?
Cool that you ask for the vibrato-loop, so I can tell that it was a lot of work to get that sounding somewhat nice
. For each individual note, I've been fine tuning the start, length and cross fading of the loop settings (in the nord sample editor). There appeared to be no particular trick, so I did just trial and error. In some notes the periods are still pretty clearly audible, in others I managed to make it quite smooth. So, if you wanna do it, just prepare yourself for an hour or so tweaking.