I typically buy non-refundable fares and thus, often have "Inactive" tickets that I can reuse by paying change fees.

I haven't tried to rebook any of these tickets since the conversion, but within the last week, have tried rebooking 4 of them, and all have proven impossible to do via the website. Sometimes, it forces a "Multi-destination" search, sometimes it says there is no routing available and sometimes it says the itinerary cannot be booked online, forcing me to call to rebook these.

Every one was rebooked with no problem via the 1K line.