Merging projects into one

Hello All. I am running Cubase pro 10 and I am having a problem merging tracks from different projects into one project.
I have 8 projects (songs) by the same band and when I attempt to either copy and paste , drag , or use import from project function , the tracks often do not line up. ie the vocals or guitars will be out of sync.

If anyone out there can help I would be appreciative.




Are there any tempo changes in the project (the original one, or the new one)? What about the Musical/Linear Timebase Settings? Is it the same for all tracks?