Is this the right place for my bug report?
I'm pretty sure.

Describe the bug
raspistill hangs on Firmware transaction timeout. After that point Xorg also hangs up. On this latest recreate, raspinfo is also hung when running after the problem to collect data.

To reproduce
Run raspistill repeatedly until the error occurs.

Expected behaviour
The kernel & firmware should remain stable at all times. Running a camera capture should always create an image and return or gracefully fail leaving the system stable.

Actual behaviour
Running raspistill repeatedly will eventually get the firmware transaction timeout.

System

raspinfo is hung after displaying the following:

$ raspinfo

System Information

Raspberry Pi 4 Model B Rev 1.2
PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"

Raspberry Pi reference 2021-01-11
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 21090519d85bdaa1615d5d5057d37b09368ea5d2, stage5

Linux projector1 5.4.83-v7l+ #1379 SMP Mon Dec 14 13:11:54 GMT 2020 armv7l GNU/Linux
Revision : c03112
Serial : 10000000e4a3851c
Model : Raspberry Pi 4 Model B Rev 1.2

I will continue to try to get the raspinfo or, failing that, will try to get the equivalent parts.

• Which model of Raspberry Pi?

Pi4B, Pi3B+

• Which OS and version (cat /etc/rpi-issue)?

Raspberry Pi reference 2021-01-11
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 21090519d85bdaa1615d5d5057d37b09368ea5d2, stage5

• Which firmware version (vcgencmd version)? vcgencmd version hangs and cannot be interrupted by ^C
• Which kernel version (uname -a)?

Linux projector1 5.4.83-v7l+ #1379 SMP Mon Dec 14 13:11:54 GMT 2020 armv7l GNU/Linux

and all subsequent levels.

Logs

dmesg.txt

Additional context
This recreate is the first time raspinfo hung.
I displaying to 2 HDMI monitors.
There are 2 USB to serial adapter cables connected but not in use during recreate.
This problem occurs in all levels following and including the Dec 14, 2020 commit.
I am running a C++ application which snaps 2 images every few seconds using these 2 commands for the 2 invocations (via system()) of raspistill:

raspistill -e jpg -w 2592 -h 1944 -t 1 -n -rot 180 -st -o /home/pi/tgt.jpg 2>&1
raspistill -e jpg -w 2592 -h 1944 -t 1 -n -rot 180 -ag 8.0 -dg 0.0 -st -o /home/pi/img.jpg 2>&1

When this problem occurs I have to either power cycle or run the following to reboot (sudo reboot seems to start rebooting, but never actually reboots):

echo s | sudo tee /proc/sysrq-trigger
echo u | sudo tee /proc/sysrq-trigger
echo b | sudo tee /proc/sysrq-trigger

No success with raspinfo - I'll recreate & see if I can collect & post the additional info.