Visible crew/equipment: When Walter walks towards Jesse's house when he hasn't shown up for work a camera and boom microphone shadow is shown on his back. (00:40:10)
Other mistake: When Walt is ringing Jesse to find out where he is, the call goes straight to voicemail. However, when he rings Jesse from inside Jesse's bedroom, the phone rings before going to voicemail. The mistake being that the call should have gone straight to voicemail. (00:41:00)
Continuity mistake: After Walt and Junior are about to go see Hank's mineral collection, Hank's front door is still open. The camera cuts to Hank for a moment as he turns his wheelchair to move down the hall and Walt and Junior soon follow. In the next shot, suddenly the front door has closed by itself. There was not enough time for Walt to have closed it and it would have been heard if he did.
Chosen answer: It is part of the ritual for la Santa Muerte. It is a sign of humility and sacrifice.
djm