Good Morning and welcome. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
I am so sorry to hear about Jacob's condition.
My fear would be that Jacob may have kidney issues but since this has been ruled out, this odd behavior could also be due to developing Diabetes which causes excessive thirst or a neurologic defect such as Dementia or other defect such as a tumor. The only way to know for sure is to have your vet perform further diagnostics such as Ultrasound and MRI to rule out a tumor or other metabolis issue such as Cushings disease that can cause this as well.
At Jacob's age, there is always a chance of a brain tumor or internal tumor that would cause this odd behavior.....seek out a specialist to know for sure.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, XXXXX XXXXX
Thank you so much, William for your kind rating. It is very much appreciated! Even though you have rated, we can still communicate. If you have other questions, please Reply. I am always happy to help. I will send you a follow up in a few days to see how Jacob is doing and if I can answer any other questions.
Have a wonderful day!