Paypal transactions not completing.

[RodG]

I downloaded a copy of the source and did a file comparison of every paypal file in the in the /includes/modules/payment.... directory and subdirectories and the ipn_main_handler.php files. They were exactly the same, so the problem has not been caused by a difference in the files.

Sweet. Knowing this narrows things down a lot.

The weirdest thing is that some of the transactions complete successfully. I could accept that there was something wrong with the implementation if it failed 100% of the time... but it doesnt.

This now points back to one thing.. It's not the ZenCart code that is causing the problem, it is something server related.

Until/Unless demonstrated otherwise this is my 'final' diagnosis. I can't imagine what else it could be.

Possible causes :
Server overload
Server software being updated or patched (bad timing)
?????

Cheers
RodG