Not all replies are showing up

I replied to a thread last night. When I replied no other replies were there, but when I opened up the same thread this morning my replies were there along with other replies in front of mine. This has made me hesitant to reply to more threads due to the fact that I don’t know if the stuff I am saying has already been said.

Has anyone else had this problem.

I’ve had a similar problem these days where I posted a reply that showed up after posting. But when I reloaded the thread it was gone.