Looks like one more reason for a steering dampener. Been there, done that, luckily without the broken swing arm and shaft. High speed on hard pack then all the sudden it got way soft. I couldn't get back on the rear fast enough. Slap left, slap right and next thing I see is the pig bouncing over me. Walked away too, albeit a bit sore.
KTM-2014 500 EXC, 2014 690R, BMW- 2015 F800 GSA, 2012 K1600 GTL, Ducati-2015 Hypermotard SP, and 16 other motorcycles in various stages of restoration.