CC 0.0.567.0 and BC 7.99.3.

At Y>255, especially around the chunk edges, BC pipes don't always connect, or take their time in autoconnnecting (not sure if it's a tick speed problem). The problem seems to get worse at greater heights. The blocks flew right out of the pipes, showing they were not actually connected.

I flew down and back up and some of the pipes connected, but I got this strange unknown block which is the shape of a mining well segment where a cobble pipe should be. I couldn't break it or identify it in WAILA.

Until it's properly fixed in BuildCraft I will probably make my own fork of it and fix it there, orcreate special mod that poatches it at runtime.

Fixed in BuildCraft/BuildCraft@9b9b10f