My 2008 had two sets of holes on the main circuit board of each channel, one set for direct outs, and the other set for inserts. It’s certainly worth opening it up and having a look, I think the direct out had two holes, and the insert three, which makes sense to me at least. It’s clear which one is in use, follow the wire from the TRS socket. I had two channels converted to insert (so I could use an MS matrix) by an engineer who was also adding 12V T mic powering to each channel for use on film locations, so I wasn’t wielding the soldering iron on this occasion. I do remember it didn’t take long – but that’s probably because I wasn’t doing the soldering.