Search field (at bottom) in Calc looses focus

we’re using CODE on an own server within our school-nextcloud.
Within Calc I want to search a special field with the small CODE search field at the (left) bottom. Not the search field of the browser (latest Chrome, FF, … in Win10pro).
But after typing some characters the focus in the search field get lost and my typing changes to the last field I’ve typed before searching. Is it a bug or a “feature”?

Thanks for any hints.

Hi Holger! Does this happen even after waiting a bit after opening the file, or only once at a short time after loading? It certainly isn’t a feature.

if I wait for nearly 15 seconds before typing and clicking anything within the sheets the focus of the search field didn’t get lost until I press “ENTER” for starting the search.
If I typed immediately, or within the first approx 10 seconds, after opening the file the focus gets lost just after typing one character. I have to “re-click” into the search field, but focus gets lost again after one more character.
Perhaps it’s a “timing problem” within display routines ?

thanks and bye