I have exactly the same issue (Delphi 11.1 on Win11).
I have tried uninstalling all of my plugins, but that seems to have no effect on the problem.
Restarting Delphi or the computer also has no effect.
It seems almost calendar-related, because it can work absolutely fine for weeks, and then it abruptly stops working and will give a crash with 100% certainty every time if I have any text selected when pressing Ctrl+Shift+F.
Once it has stopped working, it will remain non-functional for weeks until it suddenly starts working again.
The search functionality always works fine, as long as no text is selected in the editor.
Has anyone reported this issue to Embarcadero yet, or should I report it?