Just a feedback about upgrading a Xavier OTA from R32.3.1 to R32.4.2 a few days ago :
I did that upgrade according to this doc (To upgrade to new minor release).
I had almost 4GB available in my eMMC rootfs. The upgrade process downloaded about 2.5 GB, but no check was made for available disk space.
So one of the l4t components failed to install, I tried to reboot and it asked me to confirm… I did.
Upon reboot, it was failing to start the Xserver.
I connected as explained here in order to free more space (had to copy all my opencv versions to an unreliable disk).
Then I faced strange problems with Argus. I also noticed that apt cache was full of both old and new versions.
So here are the various commands I have launched and cleared my case (not sure all are required, try at your own risks):
sudo apt update
sudo apt dist-upgrade
sudo dpkg --configure -a
sudo apt dist-upgrade
sudo apt --fix-broken install
sudo apt dist-upgrade
sudo apt auto remove
sudo reboot
...
sudo apt-get clean
Hope it helps.