First thought is download corruption. Publish the checksum for your OVA that you know was tested successfully, and have users verify that hash against their copy.
I really do need to make checksum checking a support habit. I don't often ask about it.
I did not have all the users verify that it downloaded without corruption. Although the checksum is published so they may be in the practice of checking it.
I know one of the users did confirm when they initially reached out that they had gone back to validate the checksum after seeing the problem.
The other issue with the idea of download corruption is it's to consistent. Every user who's seen the problem has seen it display, and had it resolved, in exactly the same way. I think the issue is oddly to consistent for it to be download corruption.