Sorry to be slow to respond, most of the team was at a conference this week.
We have been investigating the registry server performance issues, but haven't come up with a fix yet other than to get temporary improvement by rebooting the server when things aren't working well. I checked and the server was last rebooted about a day ago. The send/receive server is on the same box, so we don't like to reboot too often.
The expert who designed the registry server is no longer with us and it's taking time for others to learn things well enough to determine where the bottleneck is.
John Wickberg
Paratext support