If the oil level is good, could you (or anyone) have put in the wrong type/spec oil during one of the last few oil changes maybe?? Admittedly, It's a bit of a long shot, but putting oil in that isn't motorcycle oil & suitable for wet clutches can produce this sorta difficulty, altho with Spyders it is more often either clutch slip under load or just a failure to go/change any gear/stay in any gear right across the board....

. but I guess failing to stay in just one gear might simply be a prelude to not staying in any gear?!? :dontknow:
So do you know what oil is in there/was put in for the last couple of changes?? Other than your problem being due to incorrect oil &/or oil level, this doesn't really sound cheap.... :sour: Sorry!

pps:
Oh, and Welcome to the Forum too! :thumbup: