top door section gets slammed into door frame when closing, due to low headroom kit issue...

Hello to all,
I just joined this forum because I'm at the end of my rope and quite desperate.
I've spent 6 days installing the best opener I could find, into my mother's garage so that she doesn't have to get cold/rained on anymore leaving the house and coming home. She's turning 70 soon and I just want her to be safe.

Anyways,  I had to install a low headroom kit (from Lowwwes model#34128ZCDLG) because the door's top section was hitting the opener's drive belt rail when attempting to open.
This kit allows the top section of the door to go along the track at a slightly lower angle as the door opens.
Everything looked great. I finished the rest of the install and adjusted the opener's opening/closing cycles appropriately.
I hit the button, the door slid smoothly/effortlessly up and along the track and stopped perfectly. I may even have gotten a little teary-eyed at overcoming this great installation challenge.
I hit the button again to close.
The door was pushed nice and smoothly back down the track and everything looked perfect... until the last 4 inches of travel. 
That's when the opener's door arm violently pushed/slammed the top section of the door forward and into the door's frame, with a loud THUD.  Then, as the opener pushed the door through its last 4 inches of travel, that top section was dragged along the door frame, sliding/scraping as the door closed completely.
The issue seems to be that the opener's door arm, when pushing the door closed, pushes that top section "forward", during the last 4" of travel, instead of pushing in a more "downward" direction. This top section moves forward due to the low headroom kit, which acts like a hinge, pushing the section away from the roller/track when the door is almost closed.
Maybe the opener's door bracket needs to be moved up, or down, or maybe the opener's door arm needs to be extended, or retracted, so that the correct angle is achieved when the opener's arm pushes the door closed.

There must be someone else out there that has gone through this same problem.  The door is balanced and everything works fine and its all lubed up and there's nothing catching on anything.

You may want to try shortening the trolley arm so it is pushing down when it comes near the end of it's travel instead of pushing forward.

Thank you for that advice  
I've stared at that thing for hours, trying to figure out what would happen if I did this, or that, or something else, or another thing.

I had ~ 3" to play with, as far as raising the door bracket that connects the trolley arm to the door, thereby shortening the trolley arm length. So I just tried it. I shortened it by 2" and tested it and it seemed better, but not quite what it should be; still slamming. So I raised that door bracket as high up on the door as I could, which shortened the trolley arm another couple inches. Tried it. It got worse. The arm slams the top section into the door frame and then the closing cycle stops completely, about 2" shy of touching the ground.

The trolley arm is 2 brackets:  1 L-shaped and 1 straight.
The L bracket comes off the door bracket, and connects to the straight bracket, which then connects to the trolley.
My L bracket comes DOWN away from the door bracket, then connects with the straight bracket going up to the trolley. In this config., it seems that the L bracket pushes the door section "Forward" and even almost "Up" when closing.
Maybe I should just try it without the L bracket at all, and just use the straight arm. That way, it is always pushing in a Downward direction.
Hmmm.....

(Or maybe I should just call it quits and pay a real professional to come and save the day. Oh wait, I spent every penny I have on this G.D. opener!)

I'll get back to y'all with an update soon.

You shouldn't have to move the door bracket. The opener arm should have holes in it so you can remove the bolts to shorten or lengthen the arm. If it's really tight you can use just the straight piece of the arm. If the straight piece is too long you may have to cut it down.

You could try calling overhead head door of america, they are awesome at helping out over the phone, might provide you with some free quick suggestions, call 888-965-3667

also try eliminating the curved arm and just using straight arm attached to top of section