LizardWizard87 Ok, I took a look at the build, and it does exactly the same for me as you've reported. Fine on the right, weird on the left. Even though I don't have the CC you used, using game columns and spandrels results in the same behavior.
To get it to behave correctly, deleting that section of the foundation/platform works to fix that. it's the only way I found to fix it too. Everything else I tried failed. I thought that I could create the look of the area where the platforms are by using short half walls but even with MOO on, I couldn't do that. The half walls wouldn't connect on the ends, and I kept getting a conflicting block clusters error. I also tried sinking the platform which didn't make any difference, the columns sank with the platform, but the spandrels didn't move. After more than a couple of hours, I couldn't find anything other than deleting that section of foundation/platform that will work to fix the issue. So, the best I can suggest is to delete it and use landscaping to hide the area. Sorry for the bad news.
Hope this helps.