Sims are missing their in-door shadow whenever they are reset
Whenever a sim is reset they will have no in-door drop shadow. This can be achieved by using the shift-click "Reset Object (Debug)" interaction or it can happen on its own when reset() is called on a sim, the later can happen on its own because of error mitigation.
To give a sim an in-door shadow again, the player must unload the current lot to completely unload the sim. The easiest way to achieve this is by going to "Manage World" and then go into the lot again.
While this is only a minor visual bug, resetting a sim because of an error does actually occur somewhat regularly. In my testing, about 2 times in a 1 hour game session at max simulation speed without any further input, other than clicking away pop-ups and trying to keep the game at max speed. In these two cases reset() was called with ResetReason.RESET_ON_ERROR. Of course, resetting the sim is probably the best way to not get more problems down the line in the game, but it will make the in-door shadow disappear.
Furthermore, two very popular mods, for posing sims to then take screenshots of, always reset the sim and as such screenshots taken with them end up with out in-door shadows
There may also be more mods out there that reset sims to prevent errors.
Platform: PC
Game version: 1.120.140.1020
Mod usage: No mods required
Last exception: Bug does not generate any exceptions