Apologies, I meant a normal compression issue. We also have normal issues with morph animation at the moment so there could be a combined effect here.
It would be very helpful if you could provide other links to models where you noticed the issue (possibly by emailing support or marc @sketchfab.com in case you would prefer keeping the information private).
Regarding compressed model, there are two issues:
1. our model compression/decompression is currently "closed source"; we're talking about releasing it to the public in the future but details are not clear yet
2. our current processing pipeline is really written to output "osgjs" assets (only viewable using osgj.js to my knowledge); exporting to custom formats (especially FBX with animation) would require some changes. This is something that we might do in the future but again, this is speculative
Also 3d compression is still quite an open field (with mostly ad hoc approaches rather than widely implemented standards) and our compressed data would not look right if not correctly processed by other softwares.
Thanks a lot