Right button by trigger broke

The replacement procedure varies from controller to controller. That said, I’ve found the Model 1537, 1697, and 1708 are the common controllers used by the most amount of people. As such, my advice will be tuned to these 3 controllers.

On the Model 1537, this rarely happens; when it does you can change the triggers individually and that will fix the problem. However, it’s good to do it in a pair just in case the other isn’t far off (I’ve only seen it once on the 1537). This is not the case on Model 1697/1708; the part is a single component. Unfortunately the plastic used on the 1697 is weaker then the 1708 and is more prone to failure. This is also the one I suspect you own since you’re having an issue and I’ve seen it on this controller before.

When you are shopping for new parts, don't buy used OEM - the plastic is ridiculously brittle and prone to failure. The 3rd party ones can make problems like worn out buttons more obvious, but they aren’t as prone to breaking as the original. They are easily found on eBay, but most of them come from China unless you order a kit (even if you don’t need it). I have narrowed it down to US sellers for you, but few of them are sold in the US with just the buttons you need. If you want to get back to gaming quickly, I'd buy another controller to use for a month until the new ones show up if you order it from China; at which point you can repair the other controller and have 2. You may also find 1708 is a much better controller as I did when I got the first one I repaired - I much prefer it over the 1537/1697 at this point.

If your Xbox One Wireless Controller has sticky or broken buttons, see the Xbox One Wireless Controller Has Sticky Buttons problem page for possible problems and solutions.