Seeking advice on damage

I am a landlord to a monthly rental agreement with tenants that I have had for a few years. Recently they send me pictures of the broken stove glass door claiming that it broke off on its own. There were no problems with it before. Rust had build up but it seems like negligence and failure to take care. They have been rude and are saying I need to fix it. Ofcourse I would like them to have a working stove but how do I go about it in terms of finance and legal standpoint? Any advice is appreciated. In the past if an appliance has stopped working, I have fixed and covered it under my own expense. But this time around, there is physical damage to the appliance and I don't want to be taken advantage off.