Trail renderer stops working?

What it says on the tin. I have trail renderers attached to two gameObjects which are parented to my main object. When instanced into the scene, the trails are drawn as expected until the object has remained stationary long enough for the trails to fade. After that, the trails fail to render. I have checked in the editor during pause, and no geometry is being generated.
No scripting is affecting the objects, and nothing changes in the scene when this transition happens.

Any ideas? Project was ported over from 1.x if that has anything to do with it (and it used to work fine).

[Edit, and btw. Yoggy's custom trail renderer works great! Just concerned that this may be a bug ]

 

Nope. Weirdly, I can sometimes bring them back to life by toggling settings in the editor (like cast/recieve shadows) etc. There's no real pattern to it. It seems like they "come to rest" in a way.

 

On its way. I have combined this with another bug I reported last week. Both are explained and steps to reproduce are detailed.

Good luck!