Upon updating my ongoing world (mixed survival/creative, survival at the time of this happening) to this snapshot and going into the nether, all the chests contained inside a house placed directly in front of the nether portal, were invisible, appeared when right clicked, but were empty, when they had previously been full of blocks (mostly nether blocks but my tool chest was empty as well). This affected a total of about ten chests. Chests in adjacent buildings were unaffected.
Linked issues
Comments

https://drive.google.com/open?id=113uXlrcXFgw_6YWTH7ad3yrnJwn7QQZl
Here we go!
EDIT: I think this may be too old of a world to reproduce with the same portal that I already built, as I hadn't built it until I got to one of the next snapshots. However it may still help you, I'm not sure! I can try and figure out if I have a world from the last snapshot before the error happened, that has the portal and the house and chests in question, if that would help more?
Where are the chests located?

The world I provided was too old of a backup and did not have the nether area or even the portal built yet-- whoops!
This one is from 18w43b. It's the most recent backup I have before the bug:
https://drive.google.com/open?id=1O657f499RkiCbOSoxt4njS_lFfeFLkEl
You should load in in the nether. To attempt to reproduce: load in 18w43b. Go northwest to the small nether village. and go through the portal at the intersection under the cliff. Go to the overworld, save and exit, and upgrade to 18w43c, and go back to the nether. The chests in the house immediately in front of the portal are the affected ones. I tried reproducing the bug myself but it didn't work like that for me again.
Are you playing on a server?

No, this is a local world that I mostly play single player. I've only even opened it up to LAN a handful of times.

same thing happened to me with some chests full of netherack in my world

Interesting that it happened with netherrack for you too, Keith. Did you lose any other blocks or just the netherrack?
Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response.
Do you have a backup of the world from an earlier version (pre 1.14)? If so, please attach (or provide a download link of) the world here so we can reproduce the issue.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki