OK, trying to fix the happiness issue has led to another issue - I cannot destroy and replace planetary upgrades made by the AI on planets that I have conquered.
Here is a link to a save on DropBox that will let you see this issue:
https://www.dropbox.com/scl/fi/9bn8v4oskxy64r5ywyjvg/Crime-Issue-Under-1.8.497102.GC4Sav?rlkey=izzsn0hg7llvva0l9m1ymk2xg&dl=0
Go to the planet named "Hough III" and look at all of the planets that feed it. You will see that the AI has filled-up every planetary upgrade slot on every planet. I want to destroy one on every planet to build an Orbital Prison, but I can't destroy any of the existing planetary upgrades. What possible reason could you have for making planetary upgrades indestructible when you allow planetary improvements to be destroyed and replaced in the planet manegement screen? Please take a look at this and make planetary upgrades replaceable.
The first screen snapshot below shows what crime looks like on Hough III. The second screen snapshot shows what the planetary upgrades on Hough III look like:

