I had said that I fixed lip motion with audio in editing, but later, when I exported the file, everything was still out of sync.

I began to suspect that the program didn't respect detach audio mismatch if I slowed the audio sideways. In my case, I shifted it to the right (delayed). When rendering the project on export, the program would bring the detach audio back in place, matching it with the image clip.

I thought, I thought, and if that were so, I could fool him.

I placed a pasted background block before the delayed audio so as not to allow it to return to its place. I extended this background to the left until it was in an edit cut.

Bingo! I was able to make the program respect what I got right in editing. The end result of the exported video finally came out as I wanted.

I will close the case. Thanks to all who have gone out of their way to help.