Non start 96 SL 500
 

Recently I was leaving a parking space and the car cut off after backing 6 ft. I restarted and it did the same, still reversing. On the third time it continued to run and operated fine. Several days later I was stranded at a local store, wouldn't start at all.(Turns over, no spark). It was taken on a rollback to a local shop that I have trusted for past work. They replaced the crank position sensor (I know, when they can't find anything) although I was told this was the code thrown. I picked it up, ran fine made several stops, starts reverses, forwards, no problem. Washed car in drive and went to back out and it died. Would restart but each time I removed my foot from the brake in reverse, it died. No similar problem in drive. Took back to shop, it started and ran flawlessly. When they went to put it inside the shop, wouldn't start. They pushed it in. Haven't found a problem,crk pos sensor code comes up again. They checked most everything. Did find worn motor mount (suggested replace both); but can't think this would cause problem. Car now started for them with no problem. Still in shop, no problems found. Any ideas? 82,000 miles.

Update. Battery died while in the shop and whould not accept a charge. Not surprised as it was at least 6 years old, but never had a problem. New battery, continued investigation, no findings, car picked up. have had the car a week now. Runs fine, no problems. Is it possible that in addition to the crank position sensor, the weak and dying battery was the problem? Motor mounts replaced. Any ideas? Thanx