It's not the first time that some physics in an unity webgl build are not working correctly on my gaming pc. however on my laptop i could jump much higher. maybe you could contact https://itch.io/profile/snapplers . I had a simmilar problem with his game https://itch.io/jam/wowie-jam-2/rate/552266 but he said, that he may found the issue. could be the same reason?