I am using solr 7.2.1
Every now & then some of the cores fail to load due to "SolrCore
Initialization Failure".
From error message it looks like the reason for failure is the core missing
some of the files:

Error opening new searcher
Caused by: java.nio.file.NoSuchFileException:

But I could not find any reason for the loss of these files.
Also downloading the missing files from the backup we maintain resolves this
Any idea what might be causing this?

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