• Forge Version: 14.23.5.2847
• BuildCraft Version (Add Hash if from github): 7.99.24.6
• Any additonal mods: JEI, Inventory Tweaks, Journey Map

To Reproduce
Steps to reproduce the behavior:

1. Place heat exchenger of any lenght
2. Connect any liquids to it and begin exchanging heat
3. Place pipe next to any part of exchanger
4. Animation stops but exchange doesn't, animation won't return until exchange ends and new one begins

I've finally released this fix in 7.99.24.7 - sorry for the delay.