I have a problem with GSC, maybe someone went through the same thing: The term that brings me the most visits is "photos gray cats" (page has the same name).
Update frequently, good serp, never a problem, everything ok.
On January 9th there were 2 problems (which still persists):
1) On GSC the search terms "photos gray cats" disappeared, but also everything that has to do with the term "gray" (gray dogs, gray pets).
2) And all the other terms about cats did not disappear but all their visits became zero in GSC panel. Only zero for cats terms (no problem with term dogs, dolphins, etc)
But the strangest thing of all is that in that period of time google ranked me better on serp (yes, even with that problem). It seems as if GSC forgot about me, but instead Google rewarded me.
Thousends searches for that term, i am thrid on serp. But GSC says "nobody clics on you"
Since that January I have no performance data from the "gray cat performance".
Clarifications that may be important (or not):
-I use Wordpress updated, without any plugin of any type
-Always updated PHP and child theme
-I did not make any previous changes of any kind in: urls / sitemap / analytics