fswebcam fails to save image after some successful repetitions

[Alden Jenkins]

This script is used to get still images with fswebcam:
#!/bin/bash

for index in {0..100}
do
    echo shot $index
    echo Time: `date +"%Y-%m-%d %T"`
    fswebcam -d v4l2:/dev/video0 -r 4096x2160 --jpeg -1 --no-banner -S 9 --verbose temp/shot.jpg
    sleep 1
done
exit

It works for some 20 to 60 repetitions, then fails every time and says "Unable to find a compatible palette format."

dmesg -T shows this at the time of the failure:
[Wed Dec 1 12:48:53 2021] usb 2-8: Set SEL for device-initiated U1 failed.
[Wed Dec 1 12:48:53 2021] usb 2-8: Set SEL for device-initiated U2 failed.
[Wed Dec 1 12:48:59 2021] usb 2-8: Set SEL for device-initiated U1 failed.
[Wed Dec 1 12:48:59 2021] usb 2-8: Set SEL for device-initiated U2 failed.
[Wed Dec 1 12:49:00 2021] uvcvideo: Failed to set UVC probe control : -32 (exp. 26).
[Wed Dec 1 12:49:00 2021] uvcvideo: Failed to set UVC probe control : -32 (exp. 26).
[Wed Dec 1 12:49:00 2021] uvcvideo: Failed to set UVC probe control : -32 (exp. 26).

release of Ubuntu:
Description: Ubuntu 18.04.6 LTS
Release: 18.04

fswebcam:
  Installed: 20140113-2
  Candidate: 20140113-2
  Version table:
 *** 20140113-2 500
        500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: fswebcam 20140113-2
ProcVersionSignature: Ubuntu 4.15.0-163.171-generic 4.15.18
Uname: Linux 4.15.0-163-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.27
Architecture: amd64
CurrentDesktop: Unity:Unity7:ubuntu
Date: Wed Dec 1 12:49:05 2021
InstallationDate: Installed on 2019-04-08 (968 days ago)
InstallationMedia: Ubuntu 16.04.5 LTS "Xenial Xerus" - Release amd64 (20180731)
SourcePackage: fswebcam
UpgradeStatus: Upgraded to bionic on 2021-09-22 (70 days ago)