Elerium production bug

Resources are consumed by a ship for its entire lifetime.  Presumably, you still have 3 prototype assassins hanging around; that's where the elerium is going.

Ships built with Elerium require the resource not just to build but as a maintenance cost.

The screenshot indicates you are mining 3 Elerium and have 3 ships that are using up this resource. You have a net of 0 Elerium resources.

Are you saying you do not have 3x Prototype Assassins M2?

okey that`s clarify I have 3 ships tnx for info

you can easily end up with NEGATIVE minerals, if you use them for trade or production of ships, and while the trade agreement is still active or the ships are still alive, your mining starbase is destroyed.  This happens to me all the time.  No consequences however, which is unfortunate.....you dont piss of your trading partner, and your ships continues to work fine.  If you want to use any "more" of that mineral, then you have to first replace the quantity owed, or your ships have to be destroyed or the trade agreement ended.

Also if you take a planet via conquest and it has a Elerium based building the building will stay and you will be negative 1 on your totals. 

so is there any point adding modules for more mining on the same starbase.

Hell yeah, to get what all men want...MORE.  I dont use durantium lately, as I've been on a beam kick, but if you love the durantium mass driver, which can be OP in numbers, then you need A LOT of Durantium.  Or lets say there is only 1 Elurium in your ZOC - and that elurium is used on a support ship to enhance beams for your fleet.  well, you can get 2, 3, 4, or even 5 resources from 1, with appropriate upgrades. Now you can have 5 fleets, each with a single support ship, or have 5 planets be practically immune to invasion with the elurium defense shield.

Its only worth getting more, if you value the resource highly.