I was editing and hitting preview showed the post as all LaTex codes. It wasn't until I forced the browser to refresh that those codes were interpreted and the LaTex output displayed.
I too have been experiencing these issues. This is only happening with the old TEX system, not the new 2 dollar signs system.
It appears the old Latex system server is having intermittent downtimes. One minute, it's offline, and another minute later, it's showing online. From what I can tell, they haven't finished their server upgrade, although they started on February 8, and I cannot imagine why it's taken this long. In the meantime, I continue to wait as I would like to keep both the old and new Latex system so the community has both options to choose.