EXS24 Seventies Kit samples suddenly stop playing?

I have used the Seventies Kit from EXS24 in a track with Logic Studio 9.1.8. The first few bars are fine after loading up the song, the 70s kick and snare samples play ok but after a few bars the snare sound drops out. When I play the kit from the keyboard, it appears that the snare drum sample isn't playing. I've checked finder and the sample is there, but it stops playing unless I completely restart Logic and open the song. It is then ok for a few bars, but again suddenly the individual samples for the snare stop playing.

If I change to another kit, all is fine. However changing back to the Seventies Kit the problem is still there. The only solution is to restart logic.

Any thoughts? Is there a way of forcing samples in EXS24 for a patch to reload? Its annoying as all other drum kit voices seem ok, except this one.