I've TCP'd many times to sit next to my GCH partner in shorthaul row 1, and yes, it requires a call that then leads to manual processing. It's not a terribly efficient system to begin with, but has been bafflingly, absurdly difficult this time around. (Yes, we're third-party nominees on each others' accounts; yes we're in the same cabin; yes, I've verified on Expertflyer that the 1A next to my partner in 1C is unoccupied on both flights). This shouldn't require multiple phone calls, and certainly not multiple phone calls of 45 minutes. Harrumph.