Is just the app that I downloaded from the appstore. I did some test at work and at home with the iphone on LTE and on WIFI and it looks like, if I have low signal on both of LTE or wifi it does that, (did it with 2 bars on each one). Here at home with 3 bars on LTE and full bars on wifi does not do it.
I only use tapatalk when sometimes it takes long to see a photo and it gives me a sign that the photo is not available. Then I go to tapatalk to see it.