There are some practical ways to boost your chances of nabbing a Pal in Palworld—for example, you can get around an initial check by throwing your sphere from behind (called a 'back bonus'). The most reliable way, however, is using a Lifmunk Effigy: Items scattered around the world that boost your capture rate. Or at least that's the idea.
The impact of the humble Lifmunk was tested by Chalenor on YouTube, who "after having to use 15 spheres on an alleged 50% capture chance" did some Palworld science. In their investigations, Chalenor found that a save file with their Lifmunk Effigies turned in was performing significantly worse than a save file with no buffs at all.
As pointed out in the video's comments, there are some issues with Chalenor's methods here even if the evidence seems compelling. For one, their sample size is small for a large-scale probability test. Secondly, Chalenor is using a variety of pals with a variety of levels and HP values, so there could be more factors at play.
On the other hand, something definitely feels funky. In a Reddit thread discussing the potential bug, a rallying cry of 'I knew it!' is downright common. Some players even note that their catch rate on the same pal visibly decreased after using an effigy. Another writes: "I had a level 27 mossanda break out four plus times at 40 health with an ultra sphere. I’m level 39." Players on the game's official Discord are reporting similar problems.
This could always just be a kind of anti-survivorship bias. People with good luck don't tend to take to forums, Discords and threads to complain about it. Anyone who has played XCOM knows that a 95% chance to hit misses more than you'd expect—that's because even though something is improbable, doesn't mean it's impossible.
The gulf between our perception of random chance and the reality of it even causes devs to use 'pseudo-RNG' to keep things feeling smooth, with code dedicated to breaking bad luck streaks.
Not to mention, games are complex machines. It could be the Lifmunk Effigies, but there could be any number of other factors mucking with the numbers behind the scenes. Something's fishy either way—so it may be best to avoid using Lifmunk Effigies for now and raise your server's capture rate instead.