v11 file not working totally in v12

[Renton Maclachlan]

I'm producing a 13 part series, and have done the first two episodes in Vegas Pro 11 - 1 is finished and 2 almost. All the others I've set going in v12. Yesterday I thought, seeing I had more to do on 2, that I should bring it into v12 and finish it in that. So I did a small amount of work and then ran through the section I'd worked on. It stopped when it came to a clip that had a route tracer showing a tramping route though some mountains. Tried it a number of times and it stopped each time. Went back to my v11 file and it works fine so will continue with that episode in v11.