After researching minimum squadron jump size 8, the tech design screen is not auto-filling jump engine size, and is kicking out a "function 1050:  object reference not set to an instance of an object", presumably in relation to that empty field for jump engine size.   

Conventional start, random stars, decimal is a decimal point, and it's reproducible—it keeps popping up after closing and re-opening the project window as well as after closing and re-starting the game.

Um, and only 9 years in.   I have research set globally to 400% if that matters.

Doesn't seem to be any problem with functionality; once I fill in the blank I can design & research jump drives.

Repair yards "repairing" mothballed ships back in to service would make the most sense, perhaps reset the training revel as well so they're not 100% ready for combat right out the yard.

There are a number of mechanics that could be used for mothballing.  However, the challenge is to make mothballing a ship a meaningful decision, rather than a way to simply reduce overall maintenance costs or a way to build a massive fleet ready for activation.  For that decision to exist, there must be a scenario where mothballing a ship turns out to have been the wrong choice.

For example, lets say it takes a year to reactivate a ship.  One scenario is alien attack and the ship is not available to fight for a year - but with the wrong mothballing rules you could have your regular navy (the same fleet you would have without mothball rules) plus a huge fleet in mothballs, so that situation is actually a lot better than before, not worse.

In principle, I think shipyards (maybe repair yards) would be needed to move ships in and out of mothballs, so that you have a meaningful decision regarding how you use that finite capacity.  This would be relatively cheap in BP but costly in time.  Even in the above scenario, you would then have to choose between building new ships or reviving old ships.  Once ships are in mothballs, there would need to be some cost and perhaps facilities involved in maintaining them in that state to avoid a massive mothball fleet.  I think the simplest mechanic would be to use existing maintenance rules/facilities, but treat the mothballed ships as smaller, perhaps 20% of their normal size/cost for maintenance purposes.

That way, you can establish a fairly sizeable mothball fleet, but by limiting to some extent your active fleet.  Also because you can only store and revive at the cost of building new, you would tend to start mothballing when you are in a less active period - which makes sense - and then you are faced with another meaningful decision in terms of whether to reactivate or build new.  Setting the right time/cost of reactivation would be key to making that a difficult choice.

Mothballing would only make sense if you planned to do it for a while, so that the cost of storing and reactivating would outweigh the long-term saving of 80% of MSP expenditure.

I currently have a game with several planets very close to stars (including mercury), where the temperature is around 360 C, and the colony cost is 2.7. Isn't that a little low? The colony cost for planets under the minimum temperature goes up much faster, mars -70 with 2.7, that's only 60 C from the species minimum. Europa at -164 has 6.41 but is still closer in temperature than mercury.