Officiallly, when he finds the shower door being faulty, he should have called you and ask for repair. I know this is not how things are done in real life, and I would have done what he did, taking the door off and re-mount it. But the rule is the rule.
But if you enforce this rule, that in the future when small defect happens, he'll just have to call you to fix instead of fixing himself, be it light bulbs or toilet plunger. You are going to be on hook for more meaningless repairs. Just be aware.
The decision is yours.