Hi there,
I understand you're having issues printing photos on your Officejet 8600 Plus printer. I will certainly do my best to assist you with this.
I appreciate all the information you posted, it makes researching a bit easier :)
At this point I feel your printer could benefit from some cleaning steps that will remove any paper dust build up or anything else that could be causing the printer not to continue feeding the photo paper. There are a few steps you've already done (such as updating the firmware) but the rest of the steps should help out!
Hope this helps, have a great day!