/execute command cant handle /setblock and /fill correct

this command will set a barrier no matter if there was a block there before even though it shouldnt. /execute @a ~ ~ ~ /setblock ~ ~-1 ~ barrier 1 keep

this command will set air instead of all types of blocks instead of just barriers:
/execute @a ~ ~ ~ /fill ~ ~1 ~ ~ ~-1 ~ air 1 barrier 1

How to recreate: use the commands