I've been using QGis for quite a few years on Mac OSX, never had a problem. Now with the current configuration of OSX Sierra + QGIS 2.18.1 many project files that ones were opening nice and smooth became quite a problem to manage.
Opening project files takes quite some time and the software crashes all the time in two conditions: when I switch on some layer or while zoomin in or out. I also tried to downgreade to QGIS 2.14.10-1 but I still experienced the same.
The problem occours on different machines (MacBook Pro, iMac) and different users. We also tried different project files of different sizes. Is anybody else experiencing the same?