snip
Third test was pretty close though, and also in the second they got very decent damage in. Also on your 180° turning test, I think the crew did not get much damage in (only watched it once though).
So I did some testing as well and have to say ullumullu is not entirely wrong. If the Maxim catches a short burst while traversing through the cone and the models manage to hit the rear armor a couple of times, it can get a little dicey for the Kübel. I did 8 tests myself with the Kübel usually catching a small burst of the Maxim, then parking outside the cone at short to mid range and shooting. Kübel lost in one case where I drove past the crew to allow for rear armor hits, in two others he still won despite that but it was close. Also when parked at very short range, it could get a bit tough. When handled somewhat properly however and mostly front armor is shown, Kübel did a decent job. I can't say too much about range dependency, but I think the shorter the range the better for the crew, at least that would also be supported by the DPS calculator site.
In all cases however I'd say it is impossible to lose your Kübel to a Maxim crew since you can always reverse out and even if the crew won they suffered a lot. I agree on the case that Kübel is not a go-to counter for pushing up face to face and expect to win, so if there are very laney sections like Poltawa or Angermünde, Kübel might indeed not fare very well at least in these specific scenario.
But claiming that the Maxim could fend off both a flanking Kübel plus a frontal Volks squad is exaggerated, unless the OKW player is an idiot and charges with the Volks squad until it is suppressed before supporting with the Kübel. This combination will force a retreat unless you REALLY want to gamble with your Maxim.