In my game I start a timer as soon as the player is in a room.

But when the player completes the specified action the rest of the script works, but the timer refuses to disable.

I tried on the event of the player using the item, in the run script it clearly says "disable timer timername" where timername is the name of my timer

That didnt stop it, so i added it to the exit, That didnt stop it either
So i also added it as you enter the new room - Again that did not stop it.

I can't reproduce your problem. Could you post your game here?

I'm not sure on this, but maybe you need to give~use its (the Timer, its) Attribute name:

DisableTimer (Object_name.Timer_name)

for example:

DisableTimer (room.timer_1)