Problem may not be anything to do with cable, which is a standard MIDI cable and yes, it may have a limit to how much data it can carry, I'd suspect that the limit will be a LOT more that you're using.

I assume you're 'Playing' the data to send to another device. In order to Play, the XP80 will need to re-arrange the data from tracks into a single times sequence with the data from the tracks mixed but still in time order. Maybe the XP80 has a memory problem with the amount of data? How much RAM does it have? What happens if you try to play/send just one track, try a smaller one first, and work up with bigger tracks, then 2 tracks, then 3, etc. Does this get you further? Does the sequencer use a LOT of Controller data, a pedal or bender or similar, this sort of thing can add a LOT of data without you realising.

Does the data play OK just on the XP80, i.e. not sending it out via midi? If you can save the song as a midi file, can you attach it to your message on this forum (you'll need to .ZIP the midi file up), then we can check that there's nothing untoward in the midi data.

Geoff