I had an absolutely beautiful Yamaha TRB 1005 lined fretless 35" scale.
I found real difficulty in playing it and eventually traded it for a fretted TRB5.
I thought it was the scale length that was throwing me off, but now, having bought myself an Overwater Perception ProDeluxe which is also 35" and with an unmarked fingerboard, I'm beginning to suspect I just prefer unlined boards as my intonation on this neck is infinitely better than on the previous.
As I learned fretless on a Westone Thunder III Mk.2, (possibly the best bass I've ever had) perhaps my preference for unlined is understandable.
G.