Sencha Architect 3.2 sometimes gets very finicky with its rendering of forms. This one (which I've only recently started; it doesn't do much yet) only lets me look at it for half a second then disappears.
https://youtu.be/hIK6v3vu_II
My version details (I'm using Windows 8.1):
Sencha Architect
version: 3.2.0.193
channel: 3.2-stable
platform: 1.4.1.960
cmd: 5.1.2.52
framework: Ext JS 5.1.x