Honestly, a lot of rides frequently break down these days, including those that didn’t used to in the “before times.” Big offenders I’ve noticed lately are Indy, Rise of the Resistance, Big Thunder Mountain, Splash, Pirates and Jungle Cruise, RSR, Luigi’s, Incredicoaster, Toy Story, Web Slingers and Monsters Inc. Have also seen Buzz and Star Tours going down lately.
Some rides I notice that very rarely break down are Millennium Falcon Smugglers Run, Dumbo, Teacups, Carousel, Small World, Soarin, Mater and Ariel/Little Mermaid (if this one goes down it’s not usually very long).