I have a MacBook Pro (13-inch, 2016, Four Thunderbolt 3 Ports), running Sierra 10.12.3.
I am often having difficulties selecting some text, for example for copying it. This applies to all applications (email, text editor, etc.).
It's a bit difficult to explain what exactly the issue is, but about 50% of the time after selecting some text, the selection is reset after I release the mouse button.
Unfortunately I am not able to reproduce this, but maybe someone else has had this issue after upgrading to a new MBP recently? I have NOT had this issue on my previous MBP, so it must be related to either some change in the software or the trackpad.
EDIT: Upon further testing, the issue mostly seems to occur when I start the selection and then move the cursor to the right with the touchpad pressed down. If I start and then move the cursor to the left, I can 100% select the text as expected.