This feels like a good line of questioning to me: you might have lots of RAM, but postgres is configured to use it in certain ways, and might be making life hard for itself.
I don’t like that there are two UPDATE queries which look identical - that looks like it could be a scheduled task which took so long a second one got scheduled subsequently. It will be adding load in a situation where things are already not running well.
But I don’t know about how to do those tweaks.