To clarify, my 'box had a centre oil pick up fitted.
I have to Agree with DKLawson and SteveD, there is definitely a thread issue with these longer sump plugs. I wonder if minispares or the like are aware of this thread issue.
I had the exact same problem, but i thought it was a defective item. Now i see many others had the same issue.
At this point i'm wondering if thats the case to notice minispares of the problem.