Thanks guys.
I don't have a second tensioner assembly to test with, but a member of my club has sent me his old manual tensioning pulley. I will try to see if I can use it for testing.

It is definitely not the water pump as I have tried 2 brand new pumps as well as the old one. The original belt tracked straight before I started the process of changing it though

Head has not been removed. I only did valve stem seals.

 

So, the cam tower was off... could something have gotten in one of the dowel pin holes and causing one end of the cam box not to fully seat? Any leaks around the cam box?

 

Belts and chains track or are pulled in the direction of the higher force.

 

Interesting!

It is possible? Yes, but I did this with the engine on a stand and I was super careful. There are no leaks around the tower and the dowels were in place.

The first thing I did when I bought it was the belt and the WP, then the car did not pass inspection due to some oil leaks and I pulled the engine. The new belt was walking towards the block before I did the tower.

I will do a careful inspection of it anyways. I'm not disregarding anything at this stage.

 

Careful inspection done. A miracle must have happened overnight because now the t-belt has decided to walk back to its original centred position. There are clear indications of this on the WP pulley where a new shoulder on the wear path is now starting to show. Only thing I've done is to run the engine for while while I was looking for leaks underneath the car. I haven't touched anything, I swear.

One thing worries me slightly though, There are some slight blistering of the very thin top rubber layer in the bottom of the valleys between the teeth. Also the front bottom edge of the valleys show a little bit of wear or alteration of colour compared to the rear edge. Is this normal when a new belt is settling in? or is my belt too tight? Should I worry that the 3 nicked teeth on the cam pulley are causing this? The nicks have been sanded and polished so no real sharp edges there.