I note that the original bug report says "mostly" on curves, and indeed, this happens for me on straight rails [0.18.32], mostly when I have a blueprint with many trains in them, such as when building an LTN depot - out of ten trains, usually 2-4 do not receive their fuel.

tehfreak: your test program passes an int to %f, which results in undefined behaviour

The mod author expressly forbids people to adopt his mod, so this is unlikely to happen until the author changes his stance.