Can't resume

[Ed hoare]

Hello. I am new to get_iplayer and am very pleased with it (many
thanks to the devs) except that I am finding it impossible to resume
recordings. Every time I try to --get something that I have previously
started downloading, I get the same error every time:
"RTMPDump 2.4 git-6230845 ... ERROR: Last tag size must be
greater/equal zero ... corrupt file!"

There is a bit more than that but I can't copy text out of my
get_iplayer console for some reason, so have saved myself some typing.
I am running Win 7/64 with g_i 2.80, installed via the automated
Windows installer (the one that downloads all necessary components).

Any ideas? Am I missing some crucial flag or command?

Thanks in advance.