Audio not lining up in editor and after exporting

Greetings,

I'm working on a very important course as a volunteer and the computer they have given me is extremely old and slow. The course is very large (about 65 slides excluding a few short quizzes also in it) and so is the amount of audio in the course. I noticed that in the audio editor the audio doesn't line up perfectly on the audio wave in the editor. It's always out sometimes as much as a cm when you select and play the audio on the time line. The more I edit the audio the more it seems to get out of line. I also noticed that when the course was exported the audio seems to have an echo to it even though the original audio files were excellent quality and very clear.

Questions:

Do you think the slow computer would cause this, is there anything else you might think would cause the audio not to line up perfectly or is this normal?

Does the program only handle so many slides of audio before complications happen?

Do you think the audio editor not lining up would cause the poor audio quality with the finished product?

Any suggestions to help with the problem?

Thanks for any information and/or assistance.