Been mucking about with the latest opt-in patch for 1.7.1 and I noticed something odd.  I hadn't been building much with most of my shipyards, as I was in-between starbase upgrades and had no need for any other ship building.  But I got to the stage of the game where I wanted to build some ships so I could erect a sensor net in my territory and I saw that most of my shipyards had an immense amount of production accumulated.  There was pretty much no way some of them should have THAT much stored, so I did some checking and it appears that Accured Manufacturing Points are being stored even when something isn't being built.

Screenshots of a Before and After (with nothing being built):

and one turn later....

The difference in Accured Points does seem to be the difference between the two.

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Doing some much deeper digging, I think I know what is going on, and it's most odd.  When a ship is being built, the Social/Military split is normal, for whatever values have been set.  But when there isn't a ship being built, the Social goes to 100% as normal (which is why folks might not have noticed it in their building queues) but the military production remains the same.  In essence "free" production points are being earned, sent to the shipyard, and being stored by that shipyard.

A pair of screenshots from a different planet (one that isn't being affected by various ideological traits):

With a ship being built:

Without a ship being built:

I am running a heavily modified game, and I did start this game under 1.7.0, but I don't think either of those things should be affecting anything.  Still, I can send in a ticket if that will help.  I'll try to replicate this behavior with a vanilla game sometime tomorrow and see if I can recreate this bug in an unmodified game.