New post changing location in thread

[mtlcore]

Ok, I try posting and get this message:
The following errors occurred when this message was submitted

Then I hit refresh and I see my post appearing BEFORE the last post that I saw.

Example

Thread contains last post X, I want to reply to that post with post Y, hit submit and get that message, i refresh and I see post Y before post X......weird

and yes the message under it says:
This post is a duplicate of a post that you have posted in the last five minutes.