I had just come back through nether portal for the first time in my survival world, it generated a new portal over 200 blocks from my original and caused an explosion. the explosion deactivated the portal, and lots of magma cubes spawned.

What i expected to happen was it to connect to my original portal.

What happened was it generated 200 blocks away, blew up, and spawned, lots of magma cubes.

It is quite hard to reproduce as it doesn't always happen. may require some trile and error