(first, sorry for bad english)
this is how i reproduce:
type in the word (such as stairs) and search for stairs related items
pull out what you want
when you pull out, it has a chance the word in the search box clear. (like become nothing) and it will go back to the state when you just open your inventory
it will have a greater chance when you hold shift and pull out a whole stack of items
i am sure this is never happen in previous version (1.7.10) and i found out that it is annoying..
check the .avi file and you will see what i mean..