A-okay! To each their own...
Everyone has their own style. I think I would stop by so they get the clue and connection (no rent in the mail means we get a Dominic visit--not an avoidable, agreed upon potential, possible some time in the future Dominic visit).
But keep in mind: it is your property.
Yes, you want proper notice to go inside but not show up at the door.
To just stop by you are within your rights to do that--there is not any tenant expectation they won't get a visit by the owner (especially if chronically late and playing hide and seek).
The tenant profile tells me they may just use your date/time appointment to be gone.... or unavailable. Again....
Your name is on the title, you pay the mortgage--so you can show up on the outside of the premises for a reasonable purpose. It is your right.... They have lease of the premises not a protective bubble to prevent you stopping by.
I am all for leaving great tenants alone for quiet enjoyment--but the catch is they have to meet their side of the deal (paying rent, following rules, responding, etc)... This seems not to be the case--hence you get to be a slightly more ubiquitous presence in their life until they follow the terms of the lease.
You could even work over there--and that may be a time to talk if they are around.
But I think you have a classic series of failed promises by them (to pay rent on time) and may want to think about a Crucial Confrontation (not violent of course--just verbal) by the book of the same title-- or start the wheels turning on getting these professional tenants on the way out.
You may have to exercise that "no muscle" some and set some expectations.
You might have a line of great tenants out there that pay on time and may wonder what took you so long when you say "bye" to these folks.
Honestly, if you are hesitant to stop by your own property without an appointment I might think about hiring out management. It may be you are more inclined to be an investor/owner (which is great) and it could be you profit from hiring the person that would already have these folks in line or long gone and getting you a worry free stream payments from your property.
Best of luck!