Do you have the latest versions of SS2 and Workshop Framework? SS2 v1.0.10 and WSFW v2.0.11
The issues you describe were fixed in the latest versions.
Affirmative
I do experience severe performance issues when building ROTC city plans. The Slog was also stuck halfway through building/upgrading. The only way I could get the settlement back to building all plots (including stairs and foundations) was to take it down entirely, select and build a basic city plan, take THAT down again and rebuild the ROTC version. The building scripts kicked me out of the cinematic mode claiming the build was finished, even though it wasn't finished at all and never completed.
Took me quite a few attempts to get it done (bill for extra headache pills and coffee needed is on the way to Kinggath :p).
Now Greentop also has some minor issues. There are tons of leftovers from the explosions laying around in the plots. Looks funny but they are not a game stopper.
The power grid also didn't complete (it rarely does entirely now btw) and there were faults within the grids in almost every settlement that upgraded its plots.
I fixed those with the power grid tools command cpg -1.
The issues described above got severe the more settlements were included in my SS2 network. So I "suspect" those to be related to the number/complexity of scripts running concurrently.
My suspicions are based on the fact that I got "update messages (a settler at X has completed...)" during the scrapping and building process.
So obviously those two areas were competing (scriptwise) with the computer's ressources. All those events add up and at finally there is no room left for my main task at that very moment (scrpping/building).
At the end of the day we are dealing with some 10yo game and code technology by a company known for its immaculate record in the field of memory management and stability
/irony
My setup should be able to handle the task decently (i9750 16GB, RTX2070, 1TB SSD) but.....
Update:
I got Tenpines cleaned up by doing the squirrel approach. Find an acorn - store(save) it - repeat. So basically many small steps with lots of saving and quitting the game to desktop and then back to where I was successful. Painful but it did the job. The last stuck parts then were deleted using place everywhere's functions (extra objects & out of limit).