Ok I'm tough on things. I haven't babied this Watch it's a daily wear but I run a desk now (Lieutenant). I wear it 5-7 days a week. I only unscrew the crown to fix the date.
I have hand wound a few times also.
My question is his normal on a watch that is 4 years old? I got the Marathon GSAR because I was told it was tough and I couldn't break it. I love it but this kinda bums me out. Should I just figure on every 3-4 years this will happen?
Also is Marathon the only place to fix it?

Does the watch have crown protectors?

Yes the crown is fine it's the Stem? I'm not a Watch guy so I don't know what it's called. The crown is intact and screws back into the Watch but the Stem is broke. It was working but has stopped now. I guess it's off to Marathon. I was just disappointed in it breaking.

Most Marathon watches just have a generic ETA 2824 movement, any competent watchmaker will have parts and be able to repair it.
A broken stem is a rarity (unless you smack it on something while it's pulled out or are ham handed when you're pulling it out).

Jack at International Watch Works can probably fix it for you quickly. IWW was at one time the US authorized service center for Marathon but I'm not sure if it still is.

[email protected]

I rarely pull it out just to adjust the date. Or time. I don't baby it but thats why I bought it!!