This sounds rather odd. Is it really only the kernel update that leads to the problem you named? You didn't rollback the whole system, but just boot with the old kernels on the same system (chosen in GRUB advanced menu), right? What was asked is quite simple: make 100% sure that the bug is in some kernel update, and nothing else. If yes, which kernel update triggers it. This has to be clarified by the reporter/tester side.