I can only be about 3 steps from the chest before it says that I am too far away. On OSI, it is 16 steps. This is from the official Wiki: https://uo.com/wiki/ultima-online-wiki/skills/remove-trap/
If the player moves more than 16 tiles away from the chest or is killed during the disarming process, the process must be restarted. The disarming process begins when a player uses Remove Trap on the chest.
If the player moves more than 16 tiles away from the chest or is killed during the disarming process, the process must be restarted. The disarming process begins when a player uses Remove Trap on the chest.