Uldc files not downloading properly

[PDC]

I have been exporting files to an authorized Lava milling center and they are having inconsistencies with downloading the files. It seems that some go through just fine but some have artifacts in the scans. The scans are clean on my end at the time of the upload to the 3M portal. Also, when they download the same file the 2nd time it will go through ok.
These scans came from the Straumann CS2 scanner using the DWOS external workflow.

Anybody got any thoughts as to the cause of this problem? Thanks.