lsmod | grep ipt
Yesterday i tried booting all the kernels I have several times (back to 7.2), but with the same result.
I kept attempting to boot from the latest kernel until it finally worked. Normally I don't reboot my COS box.
I would not know how to look at log files during boot, but I told you that I have no experience with that.
Rebooting is not an option unless absolutely required, but I refuse to reboot 20 or more times for no reason.