Need help with combo gamemode (MCPE)

so I recently made a Minecraft pvp realm (code is NKthFwMA5nA if u wana join) but I was trying to make it so that you could hold a combo easier with slow falling, I have the slow falling applied in a repeating command block but I wanted to make it so you could jump normally and fall so I made a separate command block with the command: execute u/a ~ ~ ~ detect ~ ~-1 ~ air 0 effect u/a clear. it works 80% of the time but sometimes when I jump I float down and dont have the effect applied. Ive asked about this before and someone told me to setup a hit detection system I tried setting it up multiple times and just couldn't figure it out. does anyone have an easier solution? if not maybye someone could get on my realm and try to help me out with the hit detection? Thx in advance