Difficulty exporting back to Lightroom after pre-processing in DXO Photolab

I'm using DXO Photolab to pre-process certain files before returning them to Lightroom. 

After the NR/sharpening in DXO, I click "Export to Lightroom".  I can watch the green progress bar moving across the Photolab icon. It usually gets so far and then gives up, the whole thing turning red.

Sometimes the export works successfully and the exported file appears where it should , both in the Collection DXO created for this purpose, and in the folder next to the original. 

If it does, and I examine the exported file carefully, I often find that it is corrupted - typically with a rectangular area within the image which has a network of short, coloured, straight lines running across it. (typical example attached)

Sometimes a successfuly export will only appear in the DXO Collection and not back in the original folder. 

I have been speaking to DXO about this at great length without any success. Is it a Lightroom problem?

Lightroom v12, Windows 10, DXO Photolab v5.6.