This is a major and VERY annoying bug.
Under some conditions (I'm not totally sure what), TLs 9 and 10 jumpship autofacs will try to produce huge numbers of graviton launchers for at least one and possibly several watches. Industry gets allocated to ~ 25,500% for graviton launchers, so I suspect some sort of overflow/underflow is involved. The bug seems to only occur if no yard is demanding graviton launchers from the autofac. Once the bug starts triggering it tends to continue to recur every so often (usually multiple times per period.)
The industry over-allocation pulls in huge amounts of hexacarbide, chronimium and trillum through trade routes. On the subsequent cycle, all industry on the affected planet tends to get reallocated to extraction structures, completely shutting down the autofac for a few watches.
This bug severely messes with production, accumulates a giant surplus of resources and/or graviton launchers on the autofac planet, creates additional resource surpluses on any supplying hubs, and induces resource shortages in other parts of the empire.
If the autofac is getting trillum from a hub or extractor that also supplies trillum to hazardous-type worlds, it can sometimes trigger lethal survival goods shortages on these planets by monopolizing the entire trillum supply (this is most common with consumer goods autofacs on hazardous worlds, as explained in another bug report).
This bug can also occur with TL 10 starship and ramjet autofacs; they try to produce huge numbers of Grond or HK missile launchers. Unlike jumpship autofacs, it only happens at TL 10 since the Grond and HK can't be manufactured at TL 9. Starcruisers suck so there's rarely any reason to bring a starship autofac up to TL 10.
The specific triggering condition for the graviton launcher bug seems to be if there is NOT a connected TL 10 jumpyard manufacturing Undines. 0% or nearly 0% demand gets interpreted as 25500% demand. It doesn't seem to happen if there is actual demand for graviton launchers.
also happens with basilisk cannons
This bug appears to be resolved if you put the offending item's export (from the producing planet) value to zero manually.
None of the suggestions above completely squelched the bug for me. It seemed like one or the other of my TL9 autofacs would go haywire every few minutes. I even tried manually moving my tens of thousands of graviton launchers to the producing planet, to the hub, or a shipyard and that didn't work either.
But, then I noticed that I only had a surplus of graviton launchers on the one autofac world where I was building a mix of advanced and obsolete components. And now, with every one of my TL9 autofacs building 100% advanced jumpdrives I haven't seen the bug recur. It's been a few days and there are still no graviton launchers on my autofac planets.
This is in addition to the suggestions above, and one thing I want to try sometime is just doing this on its own.
Interesting finding, lazygun. I will mention it in my guide.
Fixed in latest build.
This was indeed an integer overflow problem due to a round-off calculation.