betterportals-0.2.3
Forgelin-1.8.3
forge-1.12.2-14.23.5.2838-installer-win

I made an End Portal in creative mode, and it was displaying correctly with me looking down on the Dragon's spawn altar (although that's a pretty unusual spawn spot for the End).

I went through to the End and died by falling into the abyss (was testing another mod).

The End Portal in the Overworld is no longer showing the End, but instead some random? part of the Overworld:

I shut the game down and reloaded it again, and it's displaying the End properly again.

latest.log

Good questions :) I can test some more.

It is reproducible.

With no other mods on it doesn't happen.

With just BoP on it doesn't happen.

As it clears itself up after logging out and in, it's probably some graphics refresh thing. It's not really major enough to warrant spending more time on finding out exactly what mods or combo of mods is causing it :) Feel free to close it.

I'd prefer to keep issues open until they're fixed.

Is this reliably reproducible?

If so, please try to remove as many third-party mods as possible. I wouldn't even be surprised if it happens with just BP alone since it has been some time since I last killed myself in the end during testing.

From the screenshot it looks like the part of the world shown may be the spawn area (i.e. where you'd land if you use the end exit portal), is that correct?