Heat Transfer on Medium and High speed

Hello Guys !

I have a faulty volcano setup, there are a lot of stuff wrong with it, but it allowed me to see a bug :

So I Made a Vacuum, a drop of oil watercooled by a radiant pipe that touches my sweeper. conveyor goes around and should not interact with any of this.
On Slow speed, everything is ok, the sweeper heats a bit, then cools down with the contact of the dropplet, so all is well.
But on higher speed, the sweeper gets heat from the conveyor belt passing bellow and everything blows up.

From the looks of it, the Conveyor Bridge seems to conduct heat to the sweeper, regardless of the vacuum !
I think stuff should be consistent regardless of simultation speed, hence the bug report. the Volcano is on the middle left of my base.
Good Hunting !