Wait times issue

So here’s a thing.
Last year I programmed a show in 3.9.0.
I had one very complicated track to run, and had no timecode. I ran the cue list with Learn Timing to record Wait times, so I just had to hit go at the start and the whole track ran from that. It worked perfectly.
The other day I did the same show, so I used the same show file, but now on 3.12. The timing is now slow. By the time I’m halfway through the track the list is running noticeably behind. It’s the same track, the only thing that’s changed is the software version. I had to re-record all the wait times.