This afternoon, I was trying to type the word 'volvo' into a google search box in Safari. It echoed 'olo'. Obviously fat finger syndrome, I was missing the target button, so I tried again. Same result. No matter how careful I was, when I tapped 'v' the virtual key button containing 'v' flashed in acknowledgment, but nothing was enterred in the text box.
I fixed it by forcibly unloading and reopening safari, after which normal operation was resumed. So it was a software bug, probably with roots in memory shortage as mine's an old iPad 2. But it amused me that a virtual keyboard could have what appeared for all the world to be a mechanical fault.