I have been starting development using QT a few weeks ago and encountered a similar problem. Everything was fine, compiling the apps and deploying to the PI using QT Creator without issues. But as soon as I started the app (or wanted to debug) the app died with a Segfault.
After some hours, I noticed that libts on Jessie has been quite old. I re-installed Jessie-Lite and compiled libts on my own, directly from the GitHub repository here: lbts GitHub Repo .
Afterwards I simply followed the tutorial to cross-compile QT5 like documented in this tutorial: RaspberryPi2EGLFS
Basically I followed each step within the tutorial and the only thing I did not do, was to install any libts related packages (just check the apt-get install commands in the tutorial and don't install the libts related packages).
I know, the thread is quite old, but maybe someone will look it up.