Damage to sliding door frame - who pays?

Hi there - looking for some advice on who pays to repair an external crack to a sliding door frame. These are careful, not negligent tenants, and this is accidental damage (although they don’t know how it happened). Unsure what is a fair expectation in these circumstances in terms of repair costs? Thanks!

The deposit is for accidental damage.
How old is it?
Have you had other tenants?
Unless it is a manufacturing fault in that case it’s your responsibility
You could go halves with them


Flat is 6 years old, we have lived there, and have had one other tenant, prior to this one. Don’t think its a defect/manufacturing fault, but rather a result of closing the sliding door too hard/incorrectly.

Then if it’s an accident you can deduct from deposit or go halves with them

Super helpful to have an outside perspective on what seems fair. Thanks!

sliding doors can close with a wack., check stopper is still in place, friction will slow it down. I would go halves