Buildcraft version: 7.99.12
Forge version: 1.12.2-14.23.1.2554
Link to crashreport or log: https://pastebin.com/8TSdwcej
Singleplayer/multiplayer: Singleplayer

Additional information:

When a mining well has finished its job, it seems like it's rapidly switching from on to off. The F3 screen shows an "isComplete = true" value, which flickers to "isComplete = false" for one frame several times per second.

It also occasionally renders the mining pipe for a single frame. The bottom texture also flickers when the camera is moving, but is still (although glitchy looking) when standing still.

This only happened in my flatland testing world when it had power, but had drilled all the way down to bedrock. If it was still drilling, or if it has just been placed but didn't have any power, it worked as expected with no FPS loss or texture flickering.

F3 screen and texture: https://i.imgur.com/E6vaLD5.png

I have that exact same problem. Did you find any solution?

sadly there is no solution from a players perspective, this is an issue that needs to be fixed in the code

I can confirm that I am seeing this as well. Using Build 7.99.17-pre1. Attached is a profiler screenshot showing the hotspot.

http://www.almuramc.com/images/bc-pump-issue.png

Let me know if I can be of assistance, I have a machine setup where it is easy to replicate this issue. Scenario happens when I was using 9 pumps in a 4 chunk area in the nether pumping lots of lava. The lava lowers un-even which I think accounted for part of this issue.

Each pump that was malfunctioning added around 10ms to the servers tick time.

that would be a different problem, could you make a new ticket? also the pumps are close to each other so they are picking up fluid blocks in each other's area, that is probably causing the constant rebuilding of the queue's