I'm pretty sure 0 bytes are not written to disk. I would rather call this a flaw in the logging.
But of course it could be very likely that things are not optimal. There are multiple causes that trigger a write. Also it could be a programming problem or a race condition that is causing excessive write. So its not easy to say why it happens.

If you want to dig into this I would suggest you attempt to also log out the variable values you find in the if conditions in DownloadDataWriter.writeDownloadData().
Line 137/138, Line 158/159 and Line 181.

You might also like to multiple in Line 138 the DateUtils.MILLIS_PER_MINUTE with maybe 5 and see if it makes a difference.

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