Incident note: Spike in the search engine changed probe

src/concepts/analysis_gotchas.md

@@ -31,6 +31,7 @@ When you start to evaluate trends, be aware of events from the past that may inv
 - **May 20, 2024 - June 14, 2024** - Excessive Glean database writes degraded Fenix performance on startup, pageload, scrolling, video playback, and possibly other areas. Some metrics were disabled. See [bug 1892230](https://bugzilla.mozilla.org/show_bug.cgi?id=1892230).
 - **Apr 18, 2024** - Google began rolling out a new SERP experience on Firefox Android, which impacted standard search metrics. See [the spreadsheet](https://docs.google.com/spreadsheets/d/16Cyx_KBieRdQkSBKolivqpBaK2H-VceN9LEZcL0snHg/edit#gid=0) for more details.
 - **March 15, 2024** - Spike in clients with null default search engine (~32%) for Firefox iOS. This issue was fixed for FX 126 and above. More details can be found in this [incident report](https://docs.google.com/document/d/1iMoGOnTZZ920oth6aWbzD_npP79vSQq6OQx_bz4vFXw/edit)
+- **Feb 29 , 2024** - Spike in the [search engine changed probe](https://dictionary.telemetry.mozilla.org/apps/firefox_desktop/metrics/search_engine_default_changed) for users who had an engine update for versions >= 124 . This is due to search engine default changed probes being triggered during engine updates even when users don't actually change their default search engines post-update [bug](https://bugzilla.mozilla.org/show_bug.cgi?id=1876178). More details can be found [here](https://mozilla-hub.atlassian.net/browse/RS-1051).
 - **Jan 15 - May 1, 2024** - Legacy Telemetry pings containing os information from Arch Linux clients without the `lsb-release` package were [dropped](https://bugzilla.mozilla.org/show_bug.cgi?id=1875874).
 - **Dec 8, 2023** - (ongoing) Firefox iOS Clients coming through the French ISP Netskope report an increased number of 4xx HTTP errors on submission ([bug 1870670](https://bugzilla.mozilla.org/show_bug.cgi?id=1870670)).
 - **Dec 7, 2023** - Contextual Services data for Firefox Desktop versions 116 and up [now supplied by Glean](http://mozilla-hub.atlassian.net/browse/DSRE-1489).