What is this weird blue mark on my keyboard?

[Windows Central Question]

weird blue mark ob keyboard

There's a funny looking blue mark above the d on my keyboard, it looks a bit like the swipe thingey??

 

[someone2639]

Re: weird blue mark ob keyboard

Swipe-type again and It should disappear

 

[shaikhmuaaz_2010]

Re: weird blue mark ob keyboard

Its the bug of wp8.1. happens many time on my Lumia 520 and 535. Gone after restart the phone
from Taptalk with Lumia 535