Tor eventually hits "No running bridges" with Snowflake

Steps to reproduce:

1. Use the fresh testbuilds by dcf https://people.torproject.org/~dcf/pt-bundle/snowflake/20180321-8.0a4-4a5889af2891/
2. Start a download https://mirrors.edge.kernel.org/centos/7.4.1708/isos/x86_64/CentOS-7-x86_64-Everything-1708.iso and watch about:downloads or your Task Manager.
3. Open another instance of snowflake-client (for example in Ricochet edit the torrc in ./local/share/Ricochet/ricochet/tor with the relevant config).
4. Watch the download failing, or the receiving/s in the Task Manager go down to 0.

Doesn't seem to be reproducible with the earlier version of snowflake-client.