So I will assume the shift key had a malfunction

They were to turn it on this week but it was malfunctioning and being repaired.

Get the 10 year battery sealed ones and replace the whole device every 10 years (or earlier if they malfunction).

If you provide extinguishers you are obligated to provide proper training on it's use and in the event of a fire, where a tenant is injured attempting to contain a fire, you can be held liable.Better pray the extinguisher does not malfunction or the tenant does not use it improperly resulting in injury or death.

Tenant agrees to allow Landlord timely access to premises to do maintenance and repair.Tenant will notify Landlord in a timely manner of any damages or problems as they arise, including damages caused by Tenant, malfunction of appliances or fixtures, and water/moisture leaks and spots.Tenant will take care of the premises, keeping them clean and clear of debris.

MAINTENANCE USE AND REPORTING: Tenant shall properly use, operate and safeguard Premises, including if applicable, any landscaping, furniture, furnishings and appliances, and all mechanical, electrical, gas and plumbing fixtures, carbon monoxide devices and smoke alarms, deck, and keep them and the Premises clean, sanitary and well ventilated....Tenant shall immediately notify Landlord, in writing, of any problem, malfunction or damage with any item including carbon monoxide devices and smoke alarms on the property.

I have the keypads with a keyed deadbolt too, because I'm afraid of the pad malfunctioning or something.

The company that manages our properties (granted the company is owned by the same dingo that owns the turnkey company I work for) only charges for items when they are relevant (IE they don't mow grass in the winter, although they do shovel snow if the property is vacant)@Sriv Nava If a toilet flapper malfunctions within the first year of ownership, my investors wouldn't even see a charge from the PM company, let alone one that is $45/Hr for labor.

I used my handyman once to replace without a permit but then I got to thinking about if for some reason the tank malfunctions and causes injury, I'd be liable and insurance wouldn't pay so for the small cost compared to leaving yourself exposed, its worth having a plumber do it and pull a permit.

Because no device can be 100% reliable, you have to balance the benefit of the device in the market (people get healed) with the risk of device malfunction (worst case, people die).