[Outdated][Bug 1.14] Bottleneck "fix valves"

As you might see on the attached picture, my fab has got three parallel lines to achieve a throughput of one car per minute.
(There is also a 4th line on the right, where I produce “all inclusive” vehicles. This line has got its own resource importers and no problem at the moment.)

The problem is, that the valves are neither forwarded from their production sites (“make valves”, left side of picture), nor they are sufficiently imported.

Hence the idea of a “1 minute production” will remain an illusion…

I already encountered this issue on a previous fab. So apparently some bug regarding the import- respectively the transport priority is present.
Also tried to place the “make valves” at different sites, connected more importers and tested all import configurations.

I als tried to give the “fix valves” an own import conveyor. Result: Only a set of 4 valves was running across the conveyor. No complete fill-up of all the empty storage at the assembly sites. Thus only the amount of valves is imported, which is sufficient to build up one single car.

Thanks to a tip from another “contestant” the solution was to delete and rebuild these “fix valves sites” after loading the game.
Afterwards the stock was immediately filled up again. So my production is up again…

Probably this save&load issue occurs on other sites too (e.g. brakes, tires, wheels).