I found the old thread and installed the update suggested there.
Sorry to hear the router F/W update did not work for you, I was the party involved, it certainly worked for me and is still in service on my daughters rather long and quite heavily conjested PN VDSL2 line, has never self re-booted since.
In my case, I could positively state that the router was randomly re-booting and not being DLM re-synch'ed as the line was 24/7 monitored and recorded with DSLStats via a RPi, your issue appears to be more current line error status related and with this particular router, however, as the earlier router F/W was proven (in my case) to be an issue and Billion issued the revision specifically mentioning the random re-booting problem was certainly prudent to update as process of elimination if nothing else.
As j0hn has already mentioned, the Billion 8800NL R2 does incorporate the Broadcom budget chipset, however I have found it adequate for my particular application and the unit has given reliable service (apart from the now resolved F/W issue) for close to 2 years, considering the unit was bought S/H from the members swap forum can't complain.
Every line is unique after all, good luck with resolution.
[Moderator edited to fix the broken link that was inadvertently copied from the previous post.]