I installed a new brush assembly on my New Day Timer this week and also took the time to install a new felt seal and brass disk against the engine block because both were worn. Now the timer lever is under tension when the engine is running, wanting to return to the fully retarded position. I have to constantly hold the lever down at the operating or running position once the engine is cranked. The timer is tending to rotate clockwise when the engine is running, as if the rotating brush is pushing it internally. I've disassembled and reassembled the timer a half dozen times and it's installed correctly. Do I need the new brush assembly to "wear in" or is there a better fix of this problem?
I think what you are describing would all go anti-clockwise as that's the way the cam rotates, first thing I would try is the lever that holds the timer on, remove it and bend it a little to put more tension on the timer case.
If you will remove the timer shield it might solve your problem. I have 3 T's and none of them have the timer shield. I installed the modern oil seal to replace the felt seal in my cars and no shield. They work fine. I use an Anderson timer in one and New Days in the other two. The felt seals were OK for their time but the newer oil seals are much better.
I remember when using the shield with a the New Day it seemed to that the timer would sometimes move unexpectedly. I believe I read somewhere on the forum years ago that the shield caused that issue. It turned out that in my case it also caused the same issue.