Hello, your question has been moved to the relevant forum.
Generally speaking, it is best to always use the latest DNG converter. It will provide support for the most cameras, and will have the latest bug fixes and corrections for different cameras (if there are any). I don't know about your problem with that one lens. But I suspect that going back to a previous version isn't going to make any difference.
Managed to get to the boittom of what was going on (also had assistance from Forum members on www.dyxum.com): before proceeding with the conversion there is a Preferences dialogue you can select that allows you to set the relevant DNG conversion for the ACR you are running. I reset this to be compatible with Ver 4.1 and bingo - all files proceessed without a hitch.
Thanks for moving to the right forum but I think this is now considered closed.