Further to this:
The cue point list in the export settings in Premiere looks correct.
I then click settings in the job exported to Media Encoder - it's at this point that the first two cue points (one is nav, the other event) are duplicated, one frame on.
If I delete the duplicated cue points, all seems OK BUT clicking settings again adds the duplicates again
OK, I think I've found out why - not a bug - user misunderstanding!!! (although tricky to find!)
Some of my source footage was created in After Effects. It turns out that there were a couple of cue points in the AE comp that had similar names to the cue points in Premiere - the AE comp was saved out to an AVI (with metadata enabled I think).
Premiere wasn't seeing this metadata and the cue points, but Media Encoder was (and it couldn't be deleted in ME - just kept coming back).
So - moral of the story - be careful with metadata!!!
I guess that Premiere should really show this embedded data though?
Thanks Eddie - have done so.
It did cause a lot of head scratching!