Same problem and I don't use OptiFine, and it is sad I have a big 6 hours replay of a cool build and I loose the player around 1h10m when I go inside a portal, Do you have a idea if my replay will be able to be save with a new version of replay or all the player entity stuff are never save after a portal teleportation? Anyway thank guys for this epic mod keep up the great work, I hope you find the problem soon and my replay is not broken simply a replay viewer problem ;)
Unfortunately it looks like replays recorded with 1.0.4 will contain this bug, there's nothing we could do to fix old relays in a newer version. We will however release 1.0.5 shortly which will fix this bug.