Been having this problem on and off for some time but the past week it's been really annoying.
Newsbin Pro 6.82 - Build 5142
Windows 10.0.19041.329 (Enterprise)
USP: giganews
I have roughly 400 groups, and newsbin is set to update headers every 81 minutes.
Issue detail
The issue is the headers in the Import folder will sometimes stack up, sometimes with the oldest are more than 20 hours old. There's nothing wrong with them, if I exit Newsbin, move all the files from Import to a temporary folder and feed them back in, it will read them all fine.
So I'm not sure what's going wrong, I have debug logging on and no errors appear (it does very little logging for importing headers, however).
I originally had it updating headers every 41 minutes but moved it to 81 minutes thinking that part of the problem was it didn't have enough time to process but that hasn't helped.