I have The Sims 2 Ultimate Collection, and the only mod I use is simNopke's Sim Shadow Fix mod - I've taken this mod out of the Mods folder, but the problem still persists. While not severe, whenever one of my Sims has low hygiene for about one minute, the "stink waves" that normally appear on a smelly sim suddenly disappear, and don't reappear for the rest of that play session - only showering and restarting the game will cause the "stink waves" to reappear when the sim reaches low hygiene again. It obviously isn't anything gameplay-hindering, but it is a slightly distracting bug and I'd much appreciate some help on fixing the issue.

-Dr.C.

Well you need the critical fix mods for a start and they may even help you with the issue. You do not want to play sims 2 mod free, that will tend to end in corruption.

No Sim Loaded +Smarter EP check. NSL is by Boiling Oil and he gives a link to the other by Cyjon. This stops the Super Duper Hug Bug, can fix some issues, burns off unneeded tokens.

No Corrupt death and NO Unlink on delete. Needed to stop your game corrupting itself over tombstones and death. by Pescado.

Creature Fixes if you play vampires to stop your entire game blowing up if Crumplebut gets bitten. Pescado

The Bat Box (FFS debugger) That may have an option to fix your issue. Pescado (I made a version that looks like a vase instead of a big black box)

The stuck object remover -which will remove invisible objects Pescado I think

The Sim blender -very handy to have. TwoJeffs I think

Once you have those fixes also make sure you know the things not to do that maxis left in the game.
never delete a sim from the simbin
never move sims between hoods
never move a sim (including graves) in a house into the bin
never delete a grave

No Unlink on delete will probably keep you safe from those last two but I am careful anyway.

Put your black box fix back in, that is not the cause of your issue.

Since its the UC you may need to fix it in Origin. Make a backup first.

I've added all these mods and the game detects them, but the "stink waves" still disappear.

-Dr.C.

You have to use the batbox not just install it. Click on it and see if there is an option to nuke or fix.

Did you fix your game in Origin?

Not every bug is fixable in game or at all. It may be something you can fix in simPE.

Also run Hood Checker.