In your previous, previous post (2 up) you mention that that RB seems to prefer 128 rate; I would think this is related to the driver being used.
Try the same process using the WMA format, do you see/hear the same thing?
If not it likely is happening outside RB during part of the conversion process.

Otherwise, I wish I could help more, but I haven't noticed this Delay plugin issue in RB. We put delay on vocals and guitar often enough that I think one of us would have noticed if this was occurring.


I do not work here, but the benefits are still awesome
Make your sound your own!