Use case or problem
The case-sensitive option for search is easy to toggle accidentally on touchscreens (& maybe on desktop) without noticing, which breaks subsequent searches.
But despite its prominent placement I would guess that most people don’t use it. Most search boxes people encounter — on the web, in file managers, and in the apps I’m familiar with — don’t have a case sensitivity toggle right in the search field, or even visible by default. (Clearly some people use it, tho, because there are a few help requests here looking for it.)
Proposed solution
Move the case-sensitivity toggle from the search field to the options panel with the other toggles.
Current workaround (optional)
Tap carefully.
If a search doesn’t return expected results, check if the case-sensitivity toggle is unexpectedly on.