Work WITH your tenants instead of AGAINST them.
It would save you some money.
I am sorry that I had to cancel last week’s appointment, but I was not in the mood for being dismissed with another “oh, some WD 40 will fix it” and so I wanted an expert at hand who could have explained to you what exactly the problems with those locks are. Because I can’t. I know my limitations.
Do I know how big a difference a little bit of oil can make to a lock? Hell yes. But I also found a lock in my flat that was not working properly because someone had used the wrong lubricant on it.
(17-2: that is, an unlockable door handle)