My xbox gamertag is "A Witty Retort".
A friendentered a nether portal, quickly followed by me. The screen went to building terrain, and while it did, it made the hit sound continually. It never loaded the terrain. My friend got the notification that I had died, and none of my things were on either side of the portal. The terrain never loaded and I had to turn off my xbox.
When I respanwned at my last spawn point after rebooting, I had none of my items, and they were not dropped on either side of the nether portal.
Important items lost, I would hope could get replaced:
A diamond pickaxe with Efficiency 4, Unbreaking 3, Fortune 3 and Mending
A diamond shovel with efficiency 3, unbreaking 3, and mending
A diamond sword with Smite 4 and mending
diamond boots with feather falling 4
And a shulker box which had fairly easily replaceable contents
Related issues
duplicates
Comments

If you died going from nether to overworld, did you check the coords where you would have spawned in the overworld without converting the current coords?
ie. if you go into a portal at -63, 76, -63 in the nether, you would expect to show up at -500 / -500 if it worked correctly. But check to see if you spawned instead at -63 / -63 in the overworld.
We had a player experience this same bug. It usually happens going from overworld TO nether, but there have been reports of this happening when going from nether TO overword.
In the case of the player who had this happen, they died from a slime in the oveworld at the -63 / -63 coords and their items were scattered. No portal generated at those coords.
The main ticket for this Portal Bug is https://bugs.mojang.com/browse/MCPE-54519