HQ Camera driver does not set camera ISO unless some other setting is triggered.

[biasedlogic]

Describe the bug

This is actually the bug behind #1440 , which was closed without solving.
The issue started here: showmewebcam/showmewebcam#86 and was traced to camera driver (?) not doing its job right.

Basically setting manual ISO on the camera (in my case original Pi HQ camera) does not 'take' until some other setting, irrelevant to exposure, is triggered (like setting image flip).

To reproduce
Set everything exposure related, including ISO, to manual (e.g. using camera-ctl ).
Set some realistic exposure time (like 200) to get a usable image, not too bright not too dark.
Change ISO speed. The image brightness (easiest indication of changing ISO speed when on full manual) doesn't change. It should.
Change image flip and reset it again.
The image brightness NOW reflects the ISO change done in previous step.

Expected behaviour

Changing camera ISO speed to higher, when all other settings are fixed on manual should immediately (as in: for the next picture taken) make the picture brighter, and vice versa.

Actual behaviour

Changing ISO setting gets transferred to the camera module only after changing some other setting.

System

System No.1:
Linux XXXX 5.4.73 #2 Fri Dec 11 19:30:20 UTC 2020 armv6l GNU/Linux
from: https://github.com/showmewebcam/showmewebcam
Raspberry Pi ZeroW

System No. 2:

rpi-issue:
Raspberry Pi reference 2020-02-13
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 5f884374b6ac6e155330c58caa1fb7249b8badf1, stage2

vcgencmd version:
Jan 8 2021 14:34:38
Copyright (c) 2012 Broadcom
version 194a85abd768c7334bbadc3f1911c10a7d18ed14 (clean) (release) (start_x)

uname -a
Linux ptasieradio 5.4.83+ #1379 Mon Dec 14 13:06:05 GMT 2020 armv6l GNU/Linux

Built with official image, with further instructions from https://elinux.org/RPi-Cam-Web-Interface, updated dist-updated today.