Hello David. Wellcome to the forum (I´m new too). I hope your problems with your Surface are fixed with the replacement. Please report back when you have it.
Same situation here. My first unit crashed badly ever so often. Since the SP4 has been so problematic almost for everyone from day one, I though it was a drivers / updates / configuration problem, but after trying everything I read in the forum... simply gave up and returned my unit to microsoft for a replacement.
It´s been less than a week with my new unit, and up to now, I´ve had no problems whatsoever with the replacement (statisticaly speaking, my old unit would have crashed maybe a couple of times in that period). It´s too soon to say my problem has been solved, but certainly, it looks good.
Too bad microsoft´s quality control seems so deficient. The product is simply astonishing, but the execution by MS has been less than stellar. I would have expected that a product that was suposed to make of MS some sort of "Apple like" company when it comes to fit and finish, overal quality (and PRICE!), would be treated by the company as some sort of "jewel in the crown" with the Surface Book, and tested, tested and tested again before being shipped.
So, finding a product that needed four months worth of updates to be reasonably trouble-free, a first unit that seemed taken directly from the worst days of Windows 95 (false: my W95 machines were far more stable), is not what I expected.
Two weeks ago, If my friends had been interested in a SP4, I would have recommended them to take a look at Samsung´s / Huawei´s / Asus´s version instead, so dissapointed was I with mine. If my unit continues to be this stable, I´d be happy to change my mind and recommend it again, because I think it is wonderful.
Let´s hope Microsoft learns from this experience and both SP5 and SB2 are great out of the box. If it so happens, a Surface Book 2 may be in my future, since the only thing I don´t like about my SP4, is it´s small size (7-8 hours of battery life just gets it done for me).
I cannot deny one thing: at least Microsoft has done something unthinkable not long ago: have a lot of people excited about their future hardware releases.
PS) Please excuse my poor english.
