hi Borate,
Thanks for the offer. I don't want to waste your time. As you have said, you cannot replicate the situation. I can replicate a specific instance easily by using 29.97 (NTSC) fps. Then again on other clips, 29 will work just fine, but it is unpredictable. So, to be on the safe side, I'll just use 30fps all the time and all is fine.
Thank you for your interest.
St B