Issue with big pull

I'm trying to download my whole history, and so I set the initial number of messages to something silly like 99999999

A lot of things happen fast, but the sync seems to get very stuck on this particular output:

Client stopped, re-starting with right sync token and large initialSyncLimit...

Retrieving https://matrix.org/_matrix/media/v1/download/matrix.org/GOGKtNMLsSHlCFORAosRUNwR...

ERROR while trying to sync messages: Error: socket hang up

Exiting...

When I click the link in retriving, it seems to work, so I don't understand why it is (apparently) a sticking point.

I have applied the patch that is cited in Readme.md and this message does not appear after one hour, much less! I'm happy to help debugging but I do not understand Java or JS at all.