Trade Network string out of index error

I have an inbound 810 EDI document process
A file poller runs to pick up the documents and processes them
This is used by multiple Trading Partners and it works well.

However I have one trading partner that throws errors in TN.
String index out of range: -1
The service wm.b2b.editn:getICDetail failed

Here is the strange part…
If I modify the Duns for the TP in TN and my Duns in the document stripping off the leading zeros it works just fine.

When I put the zeros back on in both places it fails.

I would suspect too many leading zeroes as a starting point.

When I copied this line from another transaction that worked I failed to notice that the ISA version was 00200
the GS version was a space

With those two elements being incorrect TN was unable to process it. I have contacted my trading partner and asked them to correct the ISA and GS

Thanks for your suggestion