I looked at your previous post and I think that must be exactly what the problem is. If a sound is saved with a sample in slot 75 and the sound is loaded in another project without a sample in slot 75 there will be no preview with the sample for that sound.

This makes sound browsing is pretty much useless for sampled sounds.

I’ve also noticed that if the current sound has synthesis turned off and a synth-only sample is previewed no sound will be heard for it either. One would think the sound would contain all of the parameters and a full sample path - not just some of the parameters and a sample slot ID.