Going through established, linked Nether portals will sometimes cause game to time out.  Game will pause on 'loading terrain' screen and, after around a minute, time out.  When game is reloaded, player appears in destination portal.

This happens randomly with normal portals that are commonly used.  

Edit: Server admin tells me that we are receiving huge lag spikes when this is occurring, then they promptly decrease after I time out.  Attached is a server message.

 Edit 2: Attached Photo of Nether portal and server logs.  Unsure which log includes incident but both are attached.