Nice to know it works... Everyone likes a happy ending.
Johnny, in all my dealings with Tmart, their regular reps are great, but I always cc the same message to Sherry Ye, who is on this board. She comes and backs up the already good customer service.
If you get the time, email Sherry your concerns, and see if that helps. In the meantime, I am happy as a lark over this light. Can't wait to go outside.. 
After two test rides on the bicycle, and the ride this morning, once in a while it will change modes on a bump. That is a long way from not working at all, and when working it would change modes on almost every bump. Now, if I can find out where it is contacting to change modes, I might be able to fix that.. I hope. But, I am keeping the light. The way it lighted up the way for me this morning in the dark, I want this.. 
Glad you were able to make the fix without having to solder.
If I had to solder, I would have been dead in the water.. Where is the gizmo that makes it change modes? In the tailcap?
No its on the driver board, typically an Atmel (or similar) SMT EPROM chip.
Often times its the battery bouncing-shifting around that momentarily disrupts power. The EPROM senses this power interrupt as a mode change flip.
You could still solder it do direct driver.. oh, solder. :/
Or make solder some brass into the hollow part.. oh, solder. :/
You see, I'm making fun of you. :)
But srsly, I'd try to make the body transfer electricity without need of a spring, I guess on that light, you'd have to remove anodization somewhere
Funny thing too, I used to be super expert at casting bullets (hot lead), but can't do jack with a little hot tin!! 
However, I am moving foward on this. Now, I know what it making the light chang modes, will try to see if I can make the battery chamber a little tighter to stop the movement..
ce, wrap the battery with masking tape. Start with one wrap around on each end to start, add on as needed. Should work like a charm.
Thanks ride, going to try that tonight..
I'm a new member, hello all.
I have this light and was having the same issue. The battery adapter moved freely about an inch inside the light. So when I pointed the head up, the adapter would slide back.
When I pointed the head down, the adapter would slide forward and tap the spring on the head. This would cause a momentary disconnect and switch modes.
I put some gauze tape around the adapter and kept it tight. Worked perfect. If your not using the adapter, I think BetweenRides has the right idea by tightening the battery and that hopefully will resolve your issue.
Once I did this, it's really not too bad of a light. Good luck.
Aloha and welcome to BLF Bigpal!
Welcome to BLF Bigpal
Hi Bigpal, welcome aboard
First off, welcome!! 
As you very well can see, this is an awesome place. Full of a lot of know-how people, and temptations to get more..
On this Beamtech. Everything works perfect now. I rode a bike this morning wth the Beamtech on board. Sheesh, hit all bumps, nothing, light stayed in the mode it was in.
I have one of my Keygos 26650 batteries dedicated to this light. I have wrapped it in tap, and the fit real tight. Also, when I use an 18650, I have adapter already wrapped with tape also. Also, something else I found out too. This is a heavy light, and with the two fish knock offs mount it would slip foward. Making the light point straight down. On another forum, they suggested I put a piece of innertube in between the bars and the mount. Works like a charm. This light stays pointed right where I aimed it, and doesn't move..
BTW, got my first flash back today. A car blinked his lights at me when I was in the other lane coming toward him. I was on blinky...
Welcome to the club, Bigpal!
mine just went dead… tried to tighten the spring …didn’t work… it still dead 
any other ideas ?