I have install more than 5-6 proxmox installs over the years like this and it was okish until now. and now maybe the issue is elsewhere but I will keep what you say in mind.You can never know for sure. Remember you have not got a "clean default" install.
If I install proxmox directly from the proxmox iso do I have the same packages available (to install later) that I get when I install over debian or are there less packages?