Bavarianguru

Hey guys, I have been having a weird issue with my wife's R500. This happens most the time. The car cranks but doesn't turn over, it almost sounds like a dead battery but the battery is %100, sometimes it catches and will turn on but most the time it cuts off and won't turn on, when the car is completely cold, it always starts just fine, if I leave the fob on cranking position for 15 seconds or so, it turns on but ESP malfunction comes on. Then I have to turn it off and on right away. I finally got it to throw check engine light and it read P0355 which is the Crankshaft sensor circuit A, I have replaced it just now(big pita-no space but done) Cranked the car and it started right away, sigh! But after I drove back home and turned it off, it wouldn't turn back on just like before and the check engine light also came back on for the same code. I have been trying to figure this problem out for a year now and so far, I have replaced the whole fuse box, and put in a new battery. I'm out of options. Anybody have an idea? Thanks in advance!!