Just got this one in my conventional start game. Here's some context.
Yesterday I did something funny. I created a ship design, set a shipyard to retool for it, then deleted the design. It complained once at the next time advance (don't remember the exact error message) but then didn't complain anymore, and when the retooling was finished it showed as "unknown ship type". I immediately set it to retool to another design, and it completed without any errors, have built a few ships of the new design since. No issues for the next 2h or so of play, then at a regular time advance (5 days) the game froze and wouldn't finish the time advance. I let it sit for 30 minutes or so, then killed it. I restarted the game right away (making a backup copy too) and played a few rounds, didn't seem to have any issues. Then stopped playing for the day.
This morning I loaded it again, and at the first time advance I get a message box with the title: Error in CreateDesign and the contents:
"Error 3201 was created by DAO.Recordset
You cannot add or change a record because a related record is needed in table 'TechSystem'
When I click OK, the same error pops up about 8-10 times in a row, then goes away.
I should mention that I haven't created any new designs recently.
Savegame available if required - made just before this error appeared.