Hey is there any chance you selected the wrong option? There are two ways to curse. One option is for curse AND alching, and one is just cursing alone (without alching). Please confirm. I selected Stun/curse spells and it seems to be working very well here:
Just for clarification, this is the option you want:
Because the [Curse + alch] will look for nature runes, and stop the bot immediately if none are found, which is what I am guessing is happening in your post.