Thank you for reply. It's great to hear it's fixed in 2.0, and there is a better workaround in 1.1 than replacing the pump.

Problem: When a pump is pumping fluid either to or from a train wagon, and a mod swaps it with another fluid-wagon entity, the pump will stop working. For cargo wagons, the inserters continue to work fine when the cargo-wagon entity is swapped. Affected mod: https://mods.factorio.com/mod/TrainMass ...