[Spencer McDonald]

First post here, and it's a weird one! I've been beating my head into every wall I have for a month now!

I've been helping a friend with his 2007 BMW Z4 3.0i auto with a weird issue where it will not start, not even crank, when turning the key 80-90% of the time and the other 20-10% of the time it will turn on no problem. When it doesn't start, it shows all proper signs of life and I can hear the engine prime/wake up, but still, no crank.

Everything we've tried has not fixed it, and this is everything we've tried:

-New battery in the car
-Replacing the key battery (twice with 2 different working key batteries)
-Replacing the EWS with a programmed one from BMW and re-syncing it to the car properly with INPA and Tool32

There is a code that comes up that could have a lot of causes, and the code is, 2f45 Interface EWS-DME. After not being able to pinpoint what the issue was, we took it to a BMW repair shop to have them diagnose the issue. they told us that the EWS was bad and needed to be replaced, which is why we ended up buying one from BMW to replace it. At the BMW mechanic's shop, he re-synced the DME and EWS saying that it might work temporarily, but not forever, Which is exactly what happened. For about a week and a half, the car would start up just fine first try every time, but after that, it slowly got less consistent over time to the point where it was the same as before. This is when we bought the new EWS. After installing it and re-syncing it, it started right up every time, but we weren't convinced since it might just be doing the same thing as before and would stop working at any time. Which is exactly what happened yesterday and why I'm making this post. I have researched far and wide on the internet and can find no one who has had this same issue!

There are a couple of things that we have found on other forums to check and try to see if they will help, and I will be doing them soon:

-Checking all of the cable connections to the DME to make sure they are seated properly
-Triggering the voltage at the starter solenoid
-possibly buying a new antenna for the ignition switch in the car
-I found a kit to do an EWS delete but I am hesitant because it is 200 bucks and I'm not fully convinced it is the EWS since a new one fresh from the factory didn't fix it.

A couple of weird things that possibly seem to make it start more often:

-Hooking the car up to a battery charger/jumper (not a battery pack one but one that plugs into the wall) or hooking it up to another car. Both seem to help but because it is random, it is very hard to tell so take it with a grain of salt.
-Possibly leaving the key in the ignition on position for a little bit also seems to maybe do something, but same as before, it feels like coincidence when either of these methods do anything.

Open to everyone and Ill keep everyone up to date on what stuff I try and what ends up fixing it! Thanks to everyone who read this!