From reading the Ultimarc website the instructions on running 2 spinners on the port 1 connections by connecting the first spinner to x1, x2 and the other to y1, y2 then in Mame choosing which to use by game has me wondering where in Mame do you make this choice and will the vertical spinner run horizontal if you do?
Official mame doesn't do it.
MameAnalog+ (see sig) can.
NoNameMame (which includes analog+ features) can.
AdvanceMame can, but is done differently.
To do it in Analog+, enable
-splitmouseaxes (for automatic, but maybe not correct splitting) or
-switchmiceaxes (to enable manual switching while in game in tab UI menu). If you are only splitting one mouse, enabling both
-splitmouseaxes &
-singlemouse should do the trick.