Landlords — what's the biggest pain about managing your rentals?

I own/manage a small portfolio myself, and I'm doing some research into the problems other small landlords deal with.

I'm especially curious about the things that:

• eat up way more time than they should

• you constantly procrastinate on

• cost you money when they go wrong

• still involve spreadsheets, emails, phone calls, or manual work

• you've tried to solve with software but haven't found anything great

Not selling anything — genuinely trying to understand what problems are most common across landlords.

How many units do you own/manage, and what's the one task or problem you'd most like to never deal with again?