Corsa C starting issue

Hello everyone new to this form,
Basically I am having trouble if my Corsa C it first started when I turned it off in traffic and the car started and then cut off after about 1 second and wouldn't start again it was just cranking and cranking. Anyway it start up eventually got it home called out the R.A.C the guy told me the computer was saying 4 errors 1 crack shaft sensor, 1 immobliser and 2 oxygen sensors. He replaced the crank shaft sensor and said that should fix the problem however the problem is still there. It's not possible to recreate the issue on demand it only happens now and again and will only happen after the car has been turned on and off in a short period of time it will never not start from cold and I noticed the way to get the car to start again is to remove the key completely and reinsert it and it will start. also the engine light with the spanner not the management light flashes when this issue occurs but disappears afterwards.

Before anyone says its the immobilizer the R.A.C guy told me to check the electronics when it happens and they all still worked fine

I don't know why but I have a strange feeling its got something to do with the fuel pump i'm not sure why though?

Any idea's appreciated thanks