OK guys, The problem with the list is identified---it has nothing to do with gmane.
The problem is that basically from the very beginning I set up a list config that includes a removal of duplicate posts. I cannot recall why we needed to do this, but there must have been a good reason. The duplicate remover program (a version of formail) was updated (as I recall due to an exploitable bug) sometimes in the Summer---and started to interact with TMDA. Indeed, when TMDA gets a confirmation to its challenge, it reinjects the original message to the list---but the newer version of the duplicate remover program discards this "duplicate" copy. This is not good, and I'll think about it (ask around); I just need to run formail conditionally dependent on a change in the reinjected message. Mate
