I agree with you @Lisa367, that it is very boring and inconvenient situation. If I may offer any suggestion and comments, here goes mine's.
There are some guests that prefere to set a precise time to arrive, and once in a while they arrive late or early then expected. It has happened to me, not only when the guest is late, but when they arrive early then expected, sometimes 1 hours in advanced.
In some cases, I think it is better not to set a pre-arranged time, and make things more flexible.
When making the appointment for checkin, I usually ask the guest to message me when they arrive in the city, meaning, before taking a taxi, bus or whatsoever. Then I can know, at least roughly, what time they will be arriving in the building. It prevents me to wait more than necessary, and the guest will not have to wait if they arrive early than expected.
Anyway, when the guest insists on pre-arranged time and arrive early or late than expected, you can mention it when reviewing the guest by saying something like - "Except for the fact that Mr/Ms ____ arrived early or late than expected for checkin with pre-arranged time, what caused me some inconvenience, everything it was ok".
In some cases, it can be a good idea to adopted the self-checkin.
https://www.airbnb.com.br/help/article/1207/what-is-self-check-in