The mod system uses the info.txt files to determine where the root folder of each mod is. So long as the rest of the folder structure matches what I stated, the mod system should be able to place a default copy of info.txt in the correct folder. If you did not have info.txt nor the correct folder structure, then the mod system should give a warning stating that the Mansion.gd file was not used to mod any file, nor tagged as a custom script.
Indeed copying the code from this mod into the bottom of the Bugfix mod should probably work, which is why I suspected that you have a larger issue. Upon hearing that there are more mods that becomes the most likely explanation. Without knowing which mods you have installed I cannot verify that there are no further conflicts. Otherwise, it would likely mean that your mod system was failing in general, which can be the result of bad paths or limited permissions.
The Debug mod does not fix problems, but it can make fixing problems a lot easier. It changes how the Godot Engine handles errors from crashing to giving error messages that list a reason, file, and line number. Note that simply because it is not crashing does not mean the problems are gone and saving a progress after an error can result in data corruption (this can happen without the Debug mod, but crashing usually prevents it). On Windows 10 you will probably need to use the Command Prompt to start the game to get access to the debug output. There are instructions provided in the topic: https://itch.io/t/1137280/debugmod-v1
I understand that you may have experience with some of this before, but I am not inclined to rely on that given the limited communications so far. I have been fixing bugs and problems related to Strive(semi-officially) and its mods for more than 3 years, during which I have been updating the mod system. I often provide assistance with understanding Strive's code and mod system to modders. The Discord (https://itch.io/t/284398/discord) is often the fastest place to get help as there are usually other modders besides myself.
I have tried installing only the Bugfix mod and this mod and there are no issues.