Why is the https certificate not working?

Question

Digital certificates

Hello dear experts.
Set up Lets Encrypt certificates using certbot.
When I set up the https certificates for the first time, I first did it for site1.com and then for the rest of site2.com , site3.com and site4.com . All on one server. Thus, for each site its own certificate and everything worked. But, after some time, I noticed that the sites that were configured after site1.com do not work and the browser says that there is a problem with the certificate. I ran through the certificates of these sites and it turned out that they belong to site1.com for some reason. For a long time I could not understand what happened. What a bug, I started googling, I didn’t google anything, but I found a way to combine all sites on one server into one certificate, I did it, everything is super, but it’s not very cool. Today I decided once again to more carefully configure MY https certificate for each site. Made. Everything worked for a while and then again!!! Again, after a few minutes, everything fell off. In short, this is what I think: this certbot is such a bastard that it somehow checks the server and if it finds several certificates for different sites there, it deletes or corrupts them, I don’t know what it does, but in the end only the very first site site1.com remains operational. Well, it’s impossible to make your own for everyone, even if you shoot yourself.
Maybe someone faced this problem, tell me what's going on?