What was called?
The R gives a quick BIB prelim signal, but then either adds a BBW or changes it to a BBW. What did they go with?
The B appears to see the result of the suspect BIB on the flyer (which is clearly a great side block) grabs for his flag, but hesitates. As the BC continues toward the sideline, B10 makes a weak block on an opponent at the shoulder, stumbles, and slides down the opponent, cutting the opponent, causing the opponent to fall to the ground. If not seen in its entirety, this block may appear to a BBW foul (it is not). About this moment, the B's flag flies in and hits the BC, which could be for either suspect foul.
Not sure why the B was so intent on getting to the sideline. After the catch, if the B would have taken a few steps toward and turning his back to B's goal line, his field of view would have opened up enough to see both blocks better. If the H is looking at the flyer on his side (which he should), then he would have seen the side block, and, if the B's flag was for the suspect BIB, the H could have called the B off of it. The U should have a good look at the suspect BBW, and, if the B's flag was for that suspect BBW, he could have called the B off of that.