Figure out why destinations get disabled after deploying #40150

After deploying #40150 (closed) in longclaw's bwauth, it disabled the web servers after 4 days.

We don't know whether there's still some bug in sbws, tor CC or it's due waiting for SS=0.

To try to figure out, we've deployed #40150 (closed) with 2 threads instead of 3 and we're also going to try to measure the uploads without waiting for SS=0 to arrive.