Why did it never form a ball or has a shine on the dough after so long for TANGZHONG whole wheat?

I feed my 100% hydration starter twice a day (12 hr apart) at 1:1:1 ratio, for I don't bake often.

It usually doubles around 4-5 hours.  Thus, I consider it to be HEALTHY!!!!  (maybe not in your opinion??)

I followed the exact ingredients and procedures up until the mixer part from the recipe posted here "100% Whole WHeat Sourdough Hokkaido Milk Bread" by Benito.

I have to ADMIT that I have not had sourdough bread making for long at all.  I normally bake 100% whole wheat breads, rolls, and bagels.  They seem OK (as a beginner, I need to pat myself on the back, :) )

I ONLY used TANGZHONG method once though by changing the entire bread flour to 50-50 from another recipe, for both my hubby and I have blood sugar problems).  I think it was successful, although I probably could use the mixer slightly longer to really get the dough to form a ball and clean up the bowl interior wall.  I was afraid to mix longer, for I was trying to follow the TIME suggestion by the recipe.  The Tangzhong dough acts very differently than regular methods with biga, poolish, and whatnot. The former formed the long silky threads yet with sticky less structured (or maybe less strength?) from the last time (the first I used TangZhong).  But at least it came to a clump after all when I ended the mixing.

Today the 2nd time with Tangzhong method, with 100% whole wheat, it could never come to a clump after the butter being added.  The recipe says "

The dough may come apart, be patient, continue to mix until it comes together before drizzling in more butter.  Once all the butter has been added and incorporated increase the speed gradually to medium.  Mix at medium until the gluten is well developed, approximately 10 mins."

Just like my first one ever for Tangzhong, before I added butter, this whole wheat one also came to a clump after 7 minute of mixing. However, after the butter being added, it could never form a clump yet flatten out, even after 25 minute of mixing with rest in between.... My mixer got so hot, and I was afraid it would be dead.......  

Anyway, I had to give up, yet I wanted to see how it would be baked.  Thus, I dumped the super sticky dough into a pan directly (impossible to do anything at this point, but I even had a hard time to take it out from the mixer bowl and transfer it to the pan).

I would just let it ferment without handling it further according to the BF + 2nd proof times......

Can anybody tell me what's wrong for my dough????

Thanks