Metzeler Tire slow leak 2016 GTL

Please allow me to lay a small foundation in this Metzeler tire issue. So July 18, 2019 dealer mounts 2 new Metzeler tires during service, 67 days and 2800 miles later on a local ride I get a warning light- low rear tire 31psi (normally at 42.5 cold). 15 minutes from home its now 29psi. Refill tire, look listen, feel, check tread, bead, valve with water and glass cleaner. No trauma, no bubbles, no hissing. Let all cool down, 13psi, next day 0 psi. Dealer says come on in. Pump tire up to 48 psi, 50 mile ride to dealer arrive at 38 psi.
Bike goes in the shop....service writer comes out to me and says we can't find the leak, a new tire is $$$.$$, I ask" will Metzeler eat the cost of a new tire, it seems defective?" I'll ask the service manager says the service writer. Service writer comes back says no, you have to call Metzeler since those are the tires you put on....I replied "you put them on" but please mount a new tire. I ask the service writer, "cant you keep the tire", when your Metzeler representative comes in you say, "I need you to refund this tire so I can pay back the customer" .It's defective, the rim is fine, the valve is fine, its mounted correctly, the air wont stay inside it the mechanic is baffled. Its a simple rule out the tire failed. The service writer said he would ask the parts guy. I asked "shall I speak to the parts guy? Service writer replied "if you want" I walked up to the man sitting behind a sign that said PARTS, I asked if he would contact Metzeler, he pointed to his left and said you must speak to the PARTS Manager. I moved down the counter to the PARTS Manager, he said you have to call Metzeler since you're the consumer, I said you purchased this tire before me. The manager asked "did we install these tires"? I replied yes, he clicked on his computer, printed out a piece of paper, asked the service writer who is the Mechanic? He shouted to the mechanic, did you check the valve stem? Its now been 4 hours....I paid my bill. The Parts Manger said he would call Metzeler. The service writer recommended I also call Metzeler, I will. They will hold onto the tire, its a RoadTec Z8 190/55ZR17 75W.
So what I am looking for is Metzeler to buy me a tire, a factory trained BMW motorcycle technician could not find out why the air won't stay inside the rubber.
Has anyone else had "service people" keep pointing to their left saying you have to ask (someone else) I can't make that decision. Everyone was polite, they even washed the motorcycle after the test ride. Well the whole journey was a long way around and I think I will consider a different make touring tire.

I question the ability of the tech. With a tire leaking that bad a leak should be simple to find. Even if they have to pull the wheel off the motorcycle and dip it into a water tank. I worked in a tire shop for a few years. I could find leaks that took months to drop the pressure just a few pounds. Flat over night? Easy!

I find it strange why this is your problem. The dealer sold and mounted the tire, it leaks, short of finding a puncture they should cover it.

I use an old plastic maple syrup squeeze bottle with dishwashing soap. The surface tension of the DW soap allows slow leaks to slowly inflate large bubbles. Stem, tread, sidewall and cast wheels.
It sounds like they wanted you to do all the work- as far as the credit. The factory trained part needs to be complimented with experience.
Good luck.
OM

The Z8 tires are possibly the worst choice for you anyway. They generally go from having plenty of tread to having cord showing within a few hundred miles, no exaggeration.
Go with a known great tire for the heavy K16 bikes, either Pirelli Angel GT, RSIII's or PR4 GT A Spec. All these tires are very well recommended and work very well in all weather and conditions for our bikes. You won't get more than 5-6k miles out of any tires anyway so might as well go with the best tires available.
Sorry you had the run around but honestly, it was a blessing because hopefully, you got better tires out of the deal.