I'm not sure how helpful this is but, can you load a pre-made sample into your sample editor edit it everso slightly and save in the exact same format with different file name, then retry it in your XV5080?

The one thing I hate about ALL samplers is the tinkering about to get the timings right.
This is something that may initially be a problem or cause of the problem.

You're probably a dab hand at sample editing so I won't preach.

good luck