Large file crash

Crashes when I try and open 20 MB file. I have 2.1 GB of free space. Opens smaller files 6 mb and is fast and responsive when it work. Unfortunately not much use to me at present as I need to open larger files. IOS 9.3.5 iPhone 6+

ScrambleEggs about DWG FastView-CAD Viewer&Editor, v2.2.1