I have just had a bit of an adventure but I solved it so I am posting here for future reference for others.
I use vero 4k with a few years old optoma projector that can do 3d.
I had not had problems playing before but with some recent updates, functionality seems to have improved and it caused me some problems - 3d was being forced to 2d for any SBS videos, but playing top/bottom was OK. I tried everything, then eventually looked at the ‘whitelist’ and saw that it was lacking SBS options, only had TAB (over/under) [which worked OK] and FramePacking (which I haven’t used) so following knowledge from
I created ~/.kodi/userdata/disp_cap_3d
720p50hz FramePacking TopBottom SidebySide
720p60hz FramePacking TopBottom SidebySide
1080p24hz FramePacking TopBottom SidebySide
1080p30hz TopBottom SidebySide
1080i50hz TopBottom SidebySide
1080i60hz TopBottom SidebySide
and sure enough it’s all playing right.
The unsolved mystery is why vero is restricting the 3d options to TAB and FP when the projector capability has SBS…