Eternity refuses to draw portals under certain conditions?

Here's what it doesn't seem to be able to do: if I have a portal into another layer, from which is visible another portal back into the layer I'm currently in, Eternity refuses to draw the second portal.

You need to use a two-way OR linked portal (linked portals are always two-way).

The original type of portal doesn't like/work with recursion in this manner.

The only way I've found to make linked portals malfunction (apart from obvious error or clashing level geometry) is having 2+ linked flat portals, with a wall portal connecting those layers. Standing in the wall portal boundaries (the 64 unit deep dummy box) will cause one of those portals to stop being rendered (HOM).

It does not happen on every setup, but I'm a bit at a loss what causes it.

I've tweaked my map ever since then. I have the feeling that other setups work, so in the meantime, I removed the link. I'm not closing the thread, though.