In that screenshot I was actually trying to zap nostr:npub137c5pd8gmhhe0njtsgwjgunc5xjr2vmzvglkgqs5sjeh972gqqxqjak37w and his comment and npub were fully loaded as far as I could tell, though it usually happens on npubs that are not fully loaded so in general that does seem to be the issue.
Npubs have been taking way longer to load lately. Sometimes if I click on their profile and then go back it will then finally load and allow me to zap, but that tactic is hit or miss.