Thank you for reporting the bug! Can you compare your jump to the jump in the gif below and let me know how much smaller your jump is (50% smaller, 25% smaller)? Thanks 
I looked into the code and I can't find anything thing that can cause jump to go smaller. I tried older version of Love2d (ver10.2) and it works fine. Linux also has no issue on jumping. Seems like an issue on Mac only, and unfortunately I do not have a Mac to test it :(
But feel free to look into the source code and see if you can find the issue. The section that controls the jump is in between line 361 and line 380 in PlayState.lua. It is a tiny section of code.
Edit: Released a possible fix! :)
Yeah nice! The gravity is not based on delta time, don’t know how I missed that.
Since vsync is on, for people who have a 60hz monitor, game will run at 60fps and gravity will be applied around 60 times per second. But I guess either you have a higher refresh rate monitor or somehow your game run higher than 60fps, which caused the gravity being applied to the character way more that it should be.