I realize FL Studio isn't listed in your DAW list but I was curious to see if there was an easy solution to this anyway.
Currently if I'm using Ultrareverb on an fx send, when I render the song offline, it seems that the plugin spits out its buffer/tail at the very beginning of the rendered file, but then behaves normally afterwards. Is this just a bug? Or a side effect of something FL Studio is doing? Or I have a setting wrong?
That's odd. Usually the DAW will call an init routine before doing an offline bounce, which should clear out all memory. It sounds like maybe this doesn't happen in FL Studio? One way to avoid this issue might be to go to the end of the song and let the buffer clear out before doing the offline bounce.