"and there is no setting to control it in BOINC's preferences".

There is, I think if you tick the "Show advanced..." box, you get to set the space or percent.

Scheduled Maint. July 18, 14:00 UTC , why complaints they reported only a beginning but no end..

oh yes, they did:

"We will be temporarily disabling the ability for World Community Grid volunteers to access the website and download/upload results at 14:00 UTC on Tuesday, July 18. The window for this outage is 6 hours; however, we estimate that the interruption to volunteer-related functions will last for approximately 30 minutes."

Obviously, there are unforeseen problems

Just crunching the last WU's here.... with machines processing WU's faster then ever - the systems need regular top ups to maintain continuity - 'just in time' works fine until there's a small glitch - then it's 'less fine'.....!! Here's hoping the techs can solve the issues facing them - good luck guys....!!!

Emphasis mine, hence why I asked asked at 15:25UTC. The file uploading seems to have continued through 15:58 UTC or so as was the reporting, but then both went and never resumed, having hundreds in PV state before reporting went at moments after 15:58:35 UTC, at least those are the times as derived from the API Result pull. Running my tool, after that time, there's been zero transacting.