Synch issue when routing one input to two tracks?

[Cirrus]

Bit of a strange one, this...

Latest 32c version, Windows 10 64 bit, RME firewire drivers.

Very quickly set up a session to record some live demos. Used an M/S stereo overhead setup on drums, and I wanted to be able to immediately stop recording and press play for the band to hear what they'd just done, without copy/ pasting the L to the R channel. Sounds lazy? Absolutely, but I was also playing an instrument and didn't want to be knocked out of right-brain mode by the computer.

So I routed the S signal input to two channels, hard panned with one side inverted on the mixer strip.

The L channel was fine, but the R channel which was recording from the same hardware input was out of synch with the rest of the channels. I didn't measure how much but it sounded like somewhere between 20-40ms (which will possibly be my system latency, I was using a 2048 sample buffer.)

Obviously there's no real need to record the same input on multiple tracks, but I was doing it to speed up my workflow in a fast moving session so I wonder if I've uncovered a bug, or there's some setting I might not be aware of that would address this?

[dustinnr]

Out on a limb for me here, but were there any plugins that need delay compensation on any of the involved channels?
If so, that could be the problem.
Plugin delay compensation requires an actual recorded track to work, so when you route to a bus (or a track enabled playing back its input, which is really the same as a bus) there's no track to read ahead, and it therefore plays behind.

If you're not using a any plugins that require delay compensation (latency = 0 on the generic plugin edit dialog), then this isn't the problem.

[Cirrus]

A good thought, but there were no plugs added to the session, and no channelstrip processing engaged.

Just for clarity, I wasn't monitoring the inputs. I was recording, then listening back as and when the band played something they wanted to hear. So we were only listening to the already recorded audio, and when I zoomed in I could see ohead R was out of synch with ohead L.