So possibly 1%? And equally possible, 0.5%? Or less. Or more. The accurate answer being we don't know.
Can't estimate the failure rate based on 54 reports on a forum. And your logic is flawed. For example:
- You assume that 5% of 2017-2019 owners are active on this forum. Point being assume without data to validate the assumption.
- You also assume the active 2017-2019 members are representative of the population. This is not true as individuals with failures are more likely to become active in a forum than individuals without. For example, look at the last 7 failures reported in the thread you link. The first post of 4 of these 7 individuals (57%) is to report their transmission failure - i.e. they become active in the forum due to the failure. This significantly skews the data, making your analysis invalid.
So not knocking your intent here - your guess is as good as any (and likely better than most others). But it is just a guess. Like 0.35% is a guess.