Help!

Every now and then one or two of the keys on my new XV-88 will "stick" in sustain. The key itself doesn't stick. But the sound will not stop. On an patch with sustain, you get the sound forever. On a patch with no sustain (like a piano), you get a really long note while the note decays. This only occurs on selected keys. The condition can be "corrected" by power cycling the synth. It seems to occur when playing notes hard (not slamming them, just hard). Do I have a sick synth?

P. Todd