I am getting the same issue(it still happens on v1.16.10), but it is only happening half of the time. I suspect that using the command in unloaded chunks causes this to happen, while if the chunk is loaded there will be no issue. A temporary solution i have found is put a chain command block after with always active, and put "/effect @a jump_boost 7 255 true" which will prevent fall damage, but if you jump before the boost runs out, you will die.
Samuel Shaaban
I am getting the same issue(it still happens on v1.16.10), but it is only happening half of the time. I suspect that using the command in unloaded chunks causes this to happen, while if the chunk is loaded there will be no issue. A temporary solution i have found is put a chain command block after with always active, and put "/effect @a jump_boost 7 255 true" which will prevent fall damage, but if you jump before the boost runs out, you will die.