ToS Trade with Trigger, OCO and Stops

Hi

Despite reading all the related material on Internet and ToS, I am having trouble understanding and executing
orders on ToS.

Basically I want to execute a long position. So I enter a Buy order for for 254.40 with OCO so that there is stop limit
order for 212.23 (to cut my losses if the stock goes down. I add a trailing stop with -4 to keep my profits

However I discovered both the sells were done and I ended with a short. I thought OCO would cancel the the stop limit

What did I do wrong and what should I have done?

This might provide some help, if you haven't already seen it - [tlc.thinkorswim.com]

If this doesn't help, I'd call the help number during business hours. It's been some time since I called them but they've always been helpful when I called.