I just sent you an email (assuming the email address in your profile is correct and accepts attachments). I attached a CCF file with clean copies of all 256 possible commands of Denon protocol, device 8.

The three Pronto Hex strings you just posted are functions 92, 94 and 90 (so you'll find clean generated pronto hex for those in that ccf under those numbers). I hope you have a decent way to import or merge from a ccf into your Pronto NG configuration.

To find the function numbers from other pronto hex strings you need this version of IrTool
[Link: remotecentral.com]
plus DecodewIR.dll
[Link: john.fine.home.comcast.net]

With DecodeIR.dll in the same directory, run IrTool and paste in each Pronto Hex sample and press decode. A pop up dialog will show you what the signal is. The function number is labeled "OBC". Ignore the "EFC" number.

If you have more signals that don't work well but are good enough to decode (as those three were) you can use the decode info to select the clean signal from the file I sent. I think those clean signals should work well, but I don't see anything wrong with the Fast Forward signal you posted and not enough wrong with the Stop signal to understand why it doesn't work.

Hopefully these clean signals will work well. If not, the problem might be something about the way your 3000 is sending the signals rather than a learning problem.