Hello,
What is happening here is when you clicking search it navigate you to the /search page and the focus is automatically goes to the search input this is why the keyboard shows up but the opened composer hide the whole page so you can’t realize what is the actual page where you are and seems nothing happened. But when you start typing it will put the text to the search input field.
I think it would be nice if the composer minimized automatically on mobile (Android) when it is navigated to an other page. 