[GALLERY] 'Content not installed' warning with all content owned

Yes, same thing. Surprised to see that it's a 5-month-old issue because i noticed this only a couple of days ago, since the March 18 update, but it could've been since the March 17 update. I have placed lots a couple of weeks ago, no problem.

I'm on PC.

I put a residential from 1 save into my library to place it later in my main save. It gave the 'Content Not Installed' message.
Nothing was placed on the lot. Just the dirt of the land was there and a red marker with ''System error'' or ''failure''. Tried in Build Mode and in Manage Worlds. Same outcome.
I sighed and thought '''lot corrupt, that's a first.'' I gave up.

Just tonight i wanted to place a little Playground from the Gallery into my main save. Same thing happened.
Then i went to here, the forum. Happy to see that i was not alone.
I repaired the game. I have all the packs. Checked if they were all activated in the Pack Selector.  

Went back to my main save and tried to place the little Playground. The moment i select it in the Library i got that ''Content Not Installed message, but i was like, we are going to place this, buddy. And it worked .... 
Weird. I don't think it was missing anything. Just a little playground with mainly stuff from the Outdoor Adventures pack.

So i was hopeful and tried that Residential from earlier again. Nope. Just dirt on the lot.
And here's my story. 

With my mods folder, without the mods folder. Doesn't matter.

Thank you for your attention to this matter...