I just started my new playthrough as a Malk, and one thing that became immediately apparent was that all of the NPC's were not moving or doing anything. I remember that I initially didn't have this issue when I started my previous Tremere character (also in Plus Patch), up until I came across the infamous bug with the screwed up doors in the Skyeline Apartments (which was the main reason why I scrapped that character and decided to start over as a Malk).

Does anyone know how to fix this issue? It's honestly really a killer for me, since it just makes the hub areas feel so much less alive and more static. If anything, I would deeply appreciate any good advice.

The only reason I know for npc's not to move is continuing a savegame when map files have been changed.
Is it possible that GoG posted an update while you were playiing this character? In that case, try to restore to a previous version and then turn auto-update off for bloodlines.

I rolled back to a previous version and started a new character, but it didn't seem to fix the issue.

Do you get some "AI node rebuilding" messages when entering new maps?

Yes!
That happens all the time, especially with the "A.I Disabled" and "Node Graph Out of Date" messages, which I remember seeing a lot in Garry's Mod.

Then this is the reason and it means that you messed up the patch installation somehow. Normally everything should work again, once this has been rebuild and you revisit the maps...

How can I fix it?

It should fix itself, like if you revisit a map the nodes are already there and the NPCs should move. If they don't, you have a more serious problem...

Seems like a very serious problem to me. Usually having to rebuild the nodegraphs doesn't prevent people from walking. The only problems I have ever encountered with nodegraph rebuilding concern things that are triggered at mapload, like the haven bum won't start the conversation.

Just to make sure, you always start the game from the same shortcut?

With the Plus Patch, I always start the game from the Unofficial Patch desktop shortcut that comes with downloading the Plus Patch (the one with the red Ankh symbol).

I FOUND HOW TO FIX IT, if the npc get STUCK in any area of ​​the game, do this:
1. Open the game and load your save.
2. Enter another building or any different area, for example if you are in Santa Monica, enter the bail boands store or any nearest building.
3. WITHOUT CLOSING THE GAME, use alt+tab and go to the game folder VtMB\Unofficial_Patch\maps\graphs
and
VtMB\CQM\maps\graphs (if you are using the clan quest mod)
4. Within those 2 folders, delete ALL the files that have your name, for example for Santa Monica, all the ones that say "hub" like the ones in the image. WITHOUT CLOSING THE GAME.
5. You return to the game using alt+tab or the mouse and return to the area where the stuck npcs were. and ready.

This worked for me when the npcs on the streets of Santa Monica stood still without moving playing CQM.