Belts and elevator stuck while connected fully

Issue description

Belts gets stuck right after game load and unpause. Double reversing one of them makes them unstuck and they move OK for a short while and then get stuck again. Is it illegal to use an elevator directly connected to a balancer? If so, why does it work for a short while?

Reproduction steps

1. Location is shown on attached screenshot "Location-screenshot.jpg". It's a gold ore dock in the center.
2. Zoom in to the 2 storages shown on attached screenshot "Belts-Not-Moving-screenshot.jpg".
3. Unpause the game and observe that the belts and the elevator are not moving.
4. Reverse one of belts TWICE. That shakes them out of the stuck state and both belts and the elevator start moving.

Game version and build number

v0.6.4d (b347)

Operating system

Windows

Attachments

CL-A714EB-People-FBR-Water-QuartzDock-Ferts.save

Files not imported: CL-A714EB-People-FBR-Water-QuartzDock-Ferts.save

Governor from Discord helped me root cause the issue. The balancer had equal INPUTS on, and the 3rd input was empty so the balancer was waiting for the gold ore in the 3rd input.