Hi, did you cut off many roots when you repotted? Some orchids just resent being disturbed and throw a bit of a hissy fit. I've noticed quite a few types of orchids will drop a few leaves after repotting. I repotted a lot of orchids a few months back and most of them dropped a few leaves.
I doubt your did anything wrong and the orchid is just reacting to being disturbed.
Someone who is knowledgeable with Burrs will no doubt come along soon
Marion