Okay, so I tried your steps;
building with my family on a different lot still had crashes.
building with an other family in the same save didn't crash.
I copied the household with the house into a new save, and on a different lot, and currently I can build with no sudden crash...
So maybe it was the lot? I did actually use a lot from a park, which I had then moved elsewhere to build my house on it. Probably a bad idea.
Hopefully it'll stay like that. Thank you very much :'))
Okay nevermind...
I tried to place a bike stand and had to try around with my bushes and flowers and it crashed again :')
