New Moen shower/tub unit not working right

I just installed a new Moen tub/shower single handle unit with all new plumbing - exactly as instructed and everything tested out ok until I attached the tub spout and water is diverting to the shower head when it should not. I used copper from the manifold down to a Shark Bite elbow (threaded) and then a pvc pipe nipple I had to make to get the right length. Everything worked great but I think the tub spout restricting too much. Sent pic and info to Moen and instead of calling me they e-mailed they were sending a new spout - came today and it was the exact same spout - tried it thinking maybe mine was defective and the replacement does the exact same thing. What can I do? Would a different brand spout possibly do better. I used all the required/recommended dimensions for placement of the manifold, shower head the spout and as said used copper where required to eliminate pressure issues instead of pex - see the pic.

my first concern is the arrow pointed up on the unit? Is it possible you have the cartridge upsidedown?

no - everything is as it should be and this is not my first bathroom plumbing job - when the spout is removed, with just the nipple coming out everything works like a charm (pic shows a different nipple but same pipe size)

Man if they ever find out in 20 - 25 years from now that shark bites are defective we will lose a lot of insurance companies.

Since you used the Sharkbite-brand fittings on copper pipe, you should remove the stiffener inserts. I believe you probably did not and the resulting flow restriction is making the inside of the copper as small as the inside of PEX pipe. Thus causing back pressure forcing the full force water flow back up the shower riser pipe. Remove the fittings connecting the tub spout drop ear elbow and the the pipe out of the bottom of the valve. Using a pliers, remove the stiffener inserts from the fittings - just pull them straight out. Re-connect everything and you should be good to go.

Thanks, never thought of that!!!! - I have ordered some new stuff and am going to also try a sharkbite 1/2 fnpt to 3/4 slipfrom the faucet manifold and run 3/4 copper down to a drop ear elbow to even further the flow and will check into removing the stiffener as you suggested
thanks again!!!

ok - parts came in (found all needed fittings on line at SupplyHouse.com) anyway - as I mentioned I went to 3/4 copper down from manifold using a 1/2 FNPT x 3/4 sharkbite adapter to the elbow: 3/4 sharkbite to FNPT threads (3/4) and made a pvc nipple 3/4 male NPT to 3/4 pvc pipe to 1/2" npt male for to to the tub spout - all a-ok now! then I capped off the shower pipe and the nipple for the tub spout and did a pressure leak test - all good. Then re-assembled everything and the progress and finish pics are attached. (oh - and I removed the plastic stiffiners from the sharkbite used with the copper this time!!!) thanks all !!!