Summary: Server side structural integrity can become incorrect and out of sync with client
Game Version: A20 (b238)
CPU Model: Intel I7 10700k
System Memory: 32 gb
GPU Model and VRAM: nVidia GTX 1660 Ti 6 GB
Screen Resolution: 1920x1080
Video Settings: Custom
Game mode: MP on TFP test server
Did you wipe old saves? unknown - TFP test server
Did you start a new game? unknown - TFP test server
Did you validate your files? Yes
Are you using any mods? Client side StashAll mod installed, but not active on TFP server
EAC on or off? On
When playing on a dedicated server, server side structural integrity can become incorrect and stay permanently out of sync with the client if blocks are destroyed and replaced. I first noticed this on my own dedicated server when a partial collapse happened but after replacing the blocks, the structure would never correctly support again. Blocks showing green to place would spontaneously collapse even after trying to recalculate SI in debug mode. If the game world and save was downloaded locally, SI was correct and the structure again held correct weight.
I have reproduced a similar problem with an elevated structure on TFPs test server (18.104.22.168:25008, coordinates 2636, 53, 3903) by undercutting the dirt from the supports and replacing it with concrete. The middle of the second floor ceiling on the west wall no longer supports blocks correctly. If you try to replace the cobblestone block, it will immediately collapse if walked on even though the client shows it as green to place the block.
Detailed steps to reproduce the bug:
1) Place a cobblestone block in the ceiling at coordinate 2633, 56, 3904
Actual result: Walk on it or place a block on it and it will collapse
Expected result: A cobblestone block here should have a very high SI rating and should be able to support other blocks.
Pastebin link for output log: https://pastebin.com/zjP64Mc9