Use of scrubbing or skipping mutes audiobook

The problem: Playing a new audiobook from Audible on iBooks on my iPhone, I reached a point in the book (around 4:30 in chapter 5) where if I scrub forward, select a later chapter, or skip forward or backward, the counter continues as if playing, but there is no sound. If I start playing before that point, it will play beyond the point and continue playing even if I pause and restart. If I skip forward or backward, it will go silent, and I have to restart at the point where there is sound. I can play the entire audiobook on my Mac without problem. At the time this occurred, I was near the end of the range of the wireless earbuds I was using. I thought at first something had gone wrong with them. I also was wearing my Apple Watch which also controls play on the iPhone.

Attempts to solve:

I deleted the audiobook from my iPhone and resynced it from my Mac.

I deleted the file from my Mac and iPhone, downloaded it again from Audible and resynced it to my iPhone.

I accidentally deleted all audiobooks from my iPhone and restored them.

I reset my iPhone and restored it from a backup. (Something I hope to never have to repeat.)

I do not know how to go to an earlier back up.

There has been no change.