I did the factory reset, as suggested, and reconfigured the modem in bridge mode. The internet speed definitely improved: Rogers speed test went from ~50Mbps to a bit over 100Mbps (I'm on a 100u plan). On a different note, the "Self-Install" greeting...
Thanks for the new firmware. It's been more than a week now and no reset has been required in bridge mode. It has only lost the WAN connection once, but recovered it by itself in a few minutes. I just have one question: the original firmware version ...