Late Thursday May 23, 2019, Google’s Webmasters Twitter account tweeted that Google is suffering a new indexing problem that is completely separate from the previous day’s indexing issue.
Google again did not provide details of what is going on. I have previously speculated that these outages have been due to an infrastructure update that wasn’t rolling out well.
I have recently heard a credible rumor (not directly from Google) that the outages are not due to an infrastructure update. What I was told was that the first series of outages were due to human error.
What I was told seems to align with what Barry at Search Engine Roundtable reported he was told that the indexing issues were unrelated to algorithmic or infrastructure updates.