BSC line problem

[Marv Noltze <mnoltze@xxxxxxxxxx>]

This is a lengthy message about a bisynch line problem that I have IBM
stumped on. My site communicates our AS400 to a remote site via a BSC
line. We use an ICF file and an online COBOL program to send and receive
small transaction files. The remote site I dial into is a PC running
commercial 3780 communication software. 
  We dial in daily to receive a small file (@30 records). This works fine.
The problem is every week we try to receive a larger file(same structure
just more records, usually 1200). This larger file fails everytime. 
My communication trace shows I get about 4 packets of data and then the
two computers go into a loop where the remote sends me a '2D' request and
mine acknowledges with a '1070'. This repeats about 10 times until the
AS400 gives up and end the transmission. The remote site's trace shows the
same series of characters being exchanged. Level 2 of IBM support says my
configuration is fine and they have no suggestions. I talked to the higher
level support for the commercial software vendor of the remote site and
they are equally stumped. Nobody has any further answers or advice. They
all say all configurations are fine.
  My question(s):
 Where do I go from here?
 Has anyone else experienced hangups with bisynch lines like this?
 I need to use a BSC line to be compatible with the remote site.
 Yes, I have reviewed the manuals but they don't offer a clue.
Thanks

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