strange text/dissolve/video layer issue

It seems that for some reason, whenever I put text on a clip or add a dissolve it alters the size of the video clip wherever the text or dissolve begins. It's like, as we play through the dissolve, right at the end the video pops to a slightly different size. im usually very good at trouble shooting but this one has me stumped and aggravated. I added some specs below, and maybe someone can help me find the problem and save me from my on going frustration, as this is a feature documentary that Im cutting with a fast approaching deadline. I added the specs just in case my issue is in my settings and maybe it would stand out to someone. anyway, thanks for your time with this matter.

VIDEO SPECS:
-The video clips are from P2 cards, shot in film cam.
-I reformat the .mxf files to: HDV 720p24
-in FCP my frame size is 1248 x 702, 24 fps
-data rate 4.1 mb

STANDARD FCP TEXT:
-23.98 fps

MY FCP SEQUENCE SETTINGS:
-frame size: 1280 x 720
-aspect ratio: HDTZ 720p (16:9)
-compressor: HDV 720p24


the strange this is that it doesn't happen on every single one, most of them, but not all of them. I don't know, Im at a loss right now. please help!

-patrick

What is 1248x702 video? I've never heard of this frame size before. This could be the problem HDV 720p is 1280x720. I would keep it 1280x720 when converting it to another codec. This could be throwing FCP off.

yes...I know! I don't why it became that frame size! is there a way that can i change it without recompressing my 70+ hours of footage?

alright, i figured out a solution...slightly aggravating solution, but at the end of the day it is a solution and it works! thanks for focusing my attention to the frame size. I had a strong feeling that it was the Fs, but of course I was hoping it was an easier fix. Im just changing the frame size of the footage that seems to react the wrong way to layers and in testing it seems right on the money. have a good one!

Great Patrick! I always try to help, as it's probably the most rewarding thing that I do.