The lava generation in the new Snapshot appears to be bugged out. There is a bug where lava is spawning a block higher than it is supposed to and isn't able to flow, so it is just creating 1 block lava spots randomly.
However, this bug is incredibly weird as it appears to only appear in that one specific part of the nether and nowhere else.
Thank you for your report!
We're actually already tracking this issue in MC-174147, so I've resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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