I have a screenshot of the error below. The text is:
2. 0. 3 Function # 1500: constraint failed
UNIQUE constraint failed:
FCT_ShipDesignComponents. SDComponentID
I was on the main window trying to save my game. I'd been playing for a few hours and hadn't saved so who knows what I did in that time to cause this.
Conventional Start, Real Stars, Decimal separator is a decimal NOT a comma. Hopefully this is a one-off. It happens every time I try to save my game but I presume when I eventually quit without saving whatever triggers the constraint won't be there anymore and this won't happen again.
I'm almost 15 years into the campaign and had just discovered an alien race who promptly blew up my survey vessel. I was playing around a lot with designing components for some kind of defensive force (still pretty new at this game so I'm not an expert at how to build a military for this yet and I'm doing a lot of trial and error). This involved creating a lot of prototypes for various things. I'd already been experimenting before this as well.
My best guess about what happened is this: A while before trying to save, I distinctly remember creating a size 4 missile launcher and then a size 4 box launcher. (With the intent of having magazine fed launchers on a missile base and attack craft using box launchers with both firing the same missile. I did this by creating the box launcher and then changing the dropdown for size and reload rate to box launcher (I didn't change anything else). I'm pretty sure I created a prototype of the box launcher but not the regular one. I thought I queued both to research. When I checked later, I noticed I had two copies of the box launcher, one researched and the other as a prototype. The regular size 4 launcher didn't exist. When I noticed this, I created another project to research a size 4 standard launcher. I've attached a screenshot of the technology screen showing duplicate launchers.
I think somehow, when trying to duplicate the launcher, the same launcher got added to the list of components twice somehow and that resulted in a duplicate component ID which is triggering a database constraint. I've tried to reproduce that behavior, but I have not been able to.
ETA: I've been trying to reproduce this but have not been able to. My experiments have been revolving around prototypes. Something I did several times was create a prototype of something and then click the create button from the screen where you design research for components rather than clicking to research prototype from the class design screen. Since the error seems to indicate a duplicate component somewhere, that's been what I've been concentrating on.
ETA2: I noticed the game looked like it had saved when I loaded the game today but when I decided to try to go ahead and continue the first thing I noticed is that I'm missing some components I'd designed and researched. Specifically, I'd built a fighter with rail guns and queued it up for manufacturing. Now the design is missing basically everything. No railgun, no beam fire control, no engine and no power plant. All of those items were researched and now they're completely gone from my list of available components. I had not built any ships with technology I had researched since the last time I saved so I can't say if anything disappeared from ships that had been constructed but the ships I did have were intact (using older technology, of course). I'm not going to mess with this save game further and will make a copy of the DB file in case you need it for troubleshooting. Let me know if you need a copy.