Loading the nvidiafb kernel module before nvidia’s modules, didn’t improve matters, on the contrary, with it I couldn’t restore the console by switching to another and then back.
So I rebuilt my kernel with nvidiafb built-in (I don’t use initrd), which gave me a framebuffer device and the scrolling problem was solved.nvidia-bug-report2.log.gz (239.1 KB)
Thank you, Lamieur, for your accurate description of the problem, and thanks Aaron for the workaround.