I don't know how the settings were changed; my young daughter may have done it. Also, I just got the new update this morning. I have to touch, then double tap every time. Also, there is a yellow line around the screen and everthimg. I've checked all settings I know of, but I can't reverse this.
Sheryl found the answer herself. Quoting her comment:
I finally found it.. My daughter must have been in the accessibiltiy settings. She had the talk back on. But I didnt realize because she also had turn off all sounds on. I dont know how that makes the tapping weird, but is fixed now.
If one has a similar effect (e.g. red borders shown), and it's not the accessibility settings, another place to look for is the development settings, which also has switches to highlight certain areas for "developer feedback" when testing an app.
I actually set this setting on myself so I could zoom into the screen whenever and where ever I wanted and when I did this, a yellow/orange line would border the screen to let me know I was in that magnification. However, I've been noticing a glitch with this tablet that's happening more frequently and this is whenever my finger is on the screen, all of a sudden it'll zoom in as if I triple tapped when I never took my finger off the screen. Well, I can't seem to do anything about the glitch so I wanted to stop the triple-tap-to-zoom feature just that I forgot how I turned it on. This post that I am replying to helped me figure out how to change it back. However, the previous answer wasn't very clear to me. I finally figured it out so I've decided to give the answer more clear for anyone that may have this problem in the future. Thank you. Take care.
I had a similar problem with a Galaxy S5 which drove me totally crazy. It was stuck in the talk back mode and required a tap followed by a quick double tap before any selection was activated.
None of the info I found online helped. I finally tried going to Accesibility → Hearing and noticed that Hearing aids was checked.
So I set turn off all sounds and unchecked hearing aids and the talk back stopped and the triple tapping ended. I went back in and set hearing aids and it still worked just fine.
I know, it doesn't make sense but that is what happened. My software version
G900PVPU1B0A6, hardware versioin