In the latest episode of the Pokémon Journeys anime, Ash and Goh tried to lift a heavy log but they could not.
Ash said it was “impossible.”
Remember, in 2006, Ash lifted a log by himself and then chucked it no sweat, so he should’ve easily been able to make this happen
In 2017's Pokémon: Sun Moon, he also wasn’t able to lift a log, which seemed like a fluke at the time. But, I guess, it’s just that the character no longer has superhuman strength.