There was a bug with Dupin running under High Sierra that distorted the buttons in a Purge dialog and made them somewhat un-responsive. I hadn't seen this in the 10.13 betas so I wasn't expecting any issues when the final release of 10.13 came out this week.
Luckily, an alert Correspondent let me know about it and I fixed it right up this morning. Current users can "Check For Update..." in Dupin's application menu or download the latest version on this page.
I've also submitted an update for Dupin Lite 2 and that should be up on the App Store in a day or so.