I have a project with just an OSM topo map and want to export it via print composer with a scale and a frame. Very basic stuff. However, at some point when trying to get some ticks for lon and lat at the borders of the map, QGIS didn't respond anymore. When opening the project, it always crashes or doesn't respond. That's not the first time I encounter this problem and not the only version of QGIS. Atm the issue occurrs in QGIS 2.18.14.
That sounds like a bug in the program. QGIS 2.18 is no longer supported, which means bugs are no longer being fixed. Update to a current version of QGIS and the issue will probably be resolved.