It may be relay related if you don't always see some people. It can be useful to check relays for people that you want to follow and ensure you share relays to make it easier to find their posts.

Likely is you just miss their posts in time. When the client opens it’s not going to download all content from the beginning of time or since you last opened because that would download too much , it would be like syncing a node. So it’s just going to get the last day or last hour and then stay ...

If they use # you could follow those #'s and that will help as well. nostr:nprofile1qqsdr79v0na6czm4kjd6zpu5l9smythza0e5v8knurqzv2hh5h4gxegpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsz8nhwden5te0dehhxarj94c82c3wwajkcmr0wfjx2u3wdejhgtcpz4mhxue69uhkummnw3ezummcw3ezuer9wchslq57ya