Tempo/Time Signature Track/Track Import Issues

I’m doing a multitrack re-mix of a prog rock song with 3 tempo & time signature changes: 4/4 at 156 bpm; 15/8 at 80 bpm and 5/4 at 83 bpm. (The song was recorded in Nuendo 4 I believe and I was able to open the Nuendo file with little issues but there was no tempo/time signature track).

I did a reference mix of the song from the Nuendo file (the time signature was at the default 4/4 and 120 bpm) and imported it into a new Cubase project file and worked out the time signature and tempo tracks with the 2-track reference mix. The tempo and time signature changes followed the mix perfectly. I then attempted to imported the individual tracks into this new project file and the playback was a mess. Individual drum tracks were out of sync with each other, etc. Any ideas?

I’m thinking of doing full new wav files starting at to the end of all tracks snd then importing these into the project with the tempo/time signature track as a work around. It will be a bit of a pain because there are 6 drum tracks; bass DI and bass amp tracks, vocals and a ton of guitar tracks, etc.

Am I missing something?