Delete both subbuildings - terrain glitch is gone.

Delete large subbuilding - still causing the glitch

Disable "fixed height" for both subbuildings - still causing the glitch

The above plus disable flatten terrain for main building - still causing the glitch

Create a new subbuilding (park building template, no stucture) with "flatten terrain" enabled - still causing the glitch

Create a new subbuilding (park building template, no stucture) with "flatten terrain" disabled - still causing the glitch



Disable flatten terrain for subbuildings and main building - still causing the glitch

Create a new subbuilding (park building template, no stucture) and main building (power plant) with "flatten terrain" disabled - still causing the glitch

Put together the default coal power plant and oil power plant (as the subbuilding) - no terrain glitch

Reimported both part using the default coal power plant and a park as templates, put them together - still causing the glitch

Tested the newly reimported parts on their own - no terrain glitch

Update

My perils with subbuildings are far from over!My power plant now works with the build in subbuildings and doesn't need the old mod for it (yay!) - but it's causing a very strange terrain glitch as seen here . The terrain glitching like this also affects water, causing flooding if it's placed near a river.The building consist of the main building (the big boxes) and two subbuildings (1x16 park with concrete on the left, 8x16 building with the smokestack on the right). Both the main building and large subbuilding are power plants (only the main building produces power, employs ppl and so on - only reason the right half doesn't use the dummy building ai is the steam doesn't activate for dummy buildings). All buildings are set to flatten terrain and for both subbuildings "fixed height" is enabled.Here's what I've tried and the results:Something seems to happen when I put them together. I am out of ideas of what to try or why it's doing this.Any help would be very much appreciated!I've taken the power plant off the workshop as this looks like it might take a while to fix. At least this way no more save games will get messed up.