BuildCraft version: 7.99.20
Forge version: forge-1.12.2-14.23.5.2796

Singleplayer or multiplayer: Singleplayer
Steps to reproduce:

1. Place a wooden fluid extraction pipe on a tank or a stone fluid pipe over a pump (T-shape)
2. have 2 stone fluid pipes going into different directions (eg to different combustion engines, IC2 machines etc)
3. some times the fluid stop flowing in both direction and the source pipe (over the pump or the the extraction pipe) is only sending fluids in one direction. For this to happen this direction needs to consumes a constant amount of fluid but less than the source can provide. All 4 parts of the source pipe are full (center, "down" to the pump and the 2 outgoing directions).

The situation can be resolved by stopping the fluid flow until all pipes are empty and starting it again - or by letting the "stuck" direction fill up (eg stop the constant slow drain). Sometimes placing another pipe next to the source pipe (so that it connects) also resets the stuck direction.

Unfortunately I'm unlikely to put much work into 1.12.2 BC ATM as I'm focused on porting to 1.15.

However a temporary workaround is to use (directional) iron pipes after every split - which should help things a bit?

Oh please fix this ASAP. This also prevents fluids to go into a maschine because they get stuck on their way to it when the fluid pipes are more complex. Sure, fluids dont go just one way, but in this case here it just creates problems and I think as we have a "pump" (the wooden extraction pipe) it is okay if it just goes one way!