Google's own guidance on core updates is consistent and unhelpful in the way honest advice often is: there is nothing to fix, because nothing was flagged as wrong. Sites that lose visibility are being reassessed relative to others, which means the recovery path is producing something genuinely more useful than the pages that replaced you, not hunting for a technical culprit.
The practical discipline around updates is measurement. Record a baseline of impressions, clicks and positions by template and by intent before an update lands, so the analysis afterwards is about which segments moved rather than a site-wide average that tells you nothing. Recovery, when it comes, usually arrives at the next update rather than in the weeks between.