Alright, so this is definitely a new bug of some sort, as I never noticed this happening before. But, for some reason, my sims now cancel their actions right after I issue them. Sadly I haven't tested (because I didn't think to) to see if this is only for continuous actions like watching TV or those that take a set amount like cooking food. It only seems to happen after I tell them to switch channels; for some reason it doesn't take effect when they join another sim in watching TV.

So, wait - is this all interactions, or just TV watching? That makes a big difference .

Also, if you're testing again, try turning on testingcheats. You'll probably get a bunch of error messages whenever the sims cancel their actions; the error message may suggest an object which could be at fault, or you may be able to find one in the error logs.

I typed boolProp testingcheatsenabled into the cheat box, but I don't get any error messages when they cancel their actions. Am I doing something wrong? Also, it appears to be for all interactions, such as dancing or playing video games.

boolProp testingCheatsEnabled true

I did add the true, I think... I'll try again.

I definitely typed in "boolProp testingCheatsEnabled true," and yet nothing happened when my sim canceled his action.

Well, it's not throwing an error then - sounds, tbh, like a mod-conflict.

Oh, no...

I know this probably isn't connected, but I recently renamed three hair mesh files because Poppet said that renaming them makes the game load faster, is that related?

No, the file renaming isn't related.
What you need to do is download the HCDU (Hack Conflict Detection Utility) from simswardrobe.com
However, if you have The Sims 2 Ultimate Collection, you have to go to C:\My Documents\EA Games and from there, change the name of the folder from The Sims 2 Ultimate Collection to "The Sims 2" for HCDU to work
After you're finished, open up the program and let it do it's thing and it will report any conflicts
(don't forget to change it's name back when you are done using HCDU!!!)

I hope that makes sense

Which is weird, because I've had them for a while and nothing like this has happened before. But thanks anyways, this seems really useful.

The thing to remember about the HCDU is, that it isn't a substitute for testing. There's conflicts it can't detect, and some of the conflicts it does detect aren't problems. So it can give you a starting place; and especially in cases where you've got two or three mods interfering with each other it can save you a lot of time by telling you which mods are strong candidates for working poorly together. You're still going to have to do a lot of tedious testing; and if the flagged mods turn out to be innocent, you may still have to do the 50/50.

The 50/50?

Excuse me, what does 50/50 mean?

It's explained at the bottom of this page:
http://simswiki.info/wiki.php?title..._Custom_Content
though you might read through some of the rest of the advice there as well.

After removing a package everything works! It doesn't fix sims that are already plagued with the bug, but I can just kill them off.

Before killing them off, have you tried resetting them or moving their households out of their homes and then back in? That sometimes fixes problems with sims.