My username is rebel_epsical This occurs on survival So basically, when you lock a chest, hoppers will no longer work. They will neither input nor output items from the chest so it is basically useless.
Could you provide video proof of this? It would definitely help us solve your problem more easily. :)
Yes, this happens to me as well. Unfortunately there isn't much that can be done, short of unlocking the chests. But after googling a bit, try doing /chopper as this may fix it, (I haven't personally tested it this works).
According to the page I googled it seemed to do the same as executing /lwc flag hopper on which allows hoppers to be used on locked chests.
