Cannot see friends posts or lies

I think it seems to be intermittent but some friends posts or likes do not show up when I go to their page. Or in my news feed. Its the same friends sometimes so its not like they are constantly changing settings. It also seems like I can see if they post on mutual friends pages. Is this a bug or setting on my side or my friends side. For example, if they wish someone a happy bday, I don't see it or like a post of a friend. I haven't tried it but not sure if we both have the mutual friend does it show up only then?

Thanks,

TIm