Ran into a bug with unions which give a weird results. It affects the current place [file below], and new baseplates. Tried disabling plugins & restarting studio, still happens. Currently using the most recent studio build.
I use unions a lot, this is the first time I’ve encountered a union issue like this. It started roughly around 6:18pm EST on 9/29/2023. Ever since then, reproduction rate is at 100%. Appears to only happen with cylinders.
UnionBugPlaceFile.rbxl (71.6 KB)
We’ve filed a ticket into our internal database for this issue, and will come back as soon as we have updates!
Thanks for flagging!
Update [10/6/2023, 7:16pm EST]:
This does fix it, but it’s a temporary solution… It’s worked on mesh detail level 4 for years 
Thank you for reaching out. Setting the “Mesh Detail Level” in the “Studio Settings” makes the studio render not the original mesh but the lowest quality mesh regarding the number of triangles. Such lower-quality (simplified) meshes are used for rendering objects in the far. So, the correct result of unioning two parts can be seen in “Level 00”. If you want to see the meshes in Studio in their original shape, you should set the “Mesh Detail Level” to either “Level 00” or “DistanceBased.” Please let us know if you have further questions or concerns.