Following up a message from Jonas Maebe to Patrick Moore:
Following is a message I sent a while ago. I finally found the problem: 
somehow, there wasn't any form of handshaking selected in ZOC's setup (nor 
hardware or software). Everything is fine again now.
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 JM> Yo Patrick!
 JM> At the time that I'm writing this, I'm uploading a 777316 bytes
 JM> file to a USR Courier VEverything with a R33/T31 connect (the
 JM> receive rate shifted from 31 to 33 after a while!). After having
 JM> downloaded a 1.9M file at 3700 cps, I wanted to upload the
 JM> aforementioned file from 777Kb (in the mean time that's completed
 JM> and I'm logged off).
 JM> Everything seemed to be OK during the upload, but when the file was
 JM> sent completely, I got the message "Correcting Transmission Error
 JM> (1)" until (8). Then the upload resumed from 218Kb. When it was
 JM> done again, I got 4 more of these messgaes, after which the
 JM> transfer resumed from 498Kb. After this transfer, again I got this
 JM> messgage twice more and it resumed from 600Kb. this time, the
 JM> transfer was successful.
 JM> How come the modem didn't react immediately when an error was
 JM> reported? I used Zmodem (the built-in version of the OS/2 version
 JM> of ZOC), with which I've never had any problems before (with 28k
 JM> connects). I "know" some errors were reported by the remote modem
 JM> during the (re)sends, because at a certain moment, the RD led would
 JM> flash (this used to be the indication the a bad packet was received
 JM> by the remote when I still used my Supra 14.4).
 JM> Is this an error in the transfer protocol (Zmodem) or in the rom?
 JM> Anyway, these are the AT%q1 and AT%q2 reports after the call (I
 JM> have an external SFM 28.8 (well, 33.6 :) using flashrom beta-23):
[modem stats cut]
Cya,
           Gamefreak 
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