See the comment on step 32 regarding the amount of alcohol to use. Too much can also cause problems.

Be careful with the alcohol! If you overdo it on the amount of alcohol you use, you run the risk of removing more than just the adhesive. The cable that connects the side button assembly is under the battery, along with the wireless charging coil. It's possible to loosen those things to the point that the battery adhesive still sticks to them, but they no longer stick to the phone case, causing you to remove more than you intend.

The IR board appears to be upside down in this photo.

Instead of a heat gun or hair dryer, I used a rice sock (http://www.wikihow.com/Make-a-Rice-Sock) to apply heat evenly across the entire back of the case while the case still sat upright for me to work on getting the battery loose. It was a lot easier than trying to heat the back of the case, then flip the case over and work feverishly before it cooled.