I occasionally have the rats nest disappear completely. The button on the left still shows "hide rats nest" so Kicad apparently thinks it is still being shown. Repeatedly pushing the hide/show button has no effect, the rats nest remains invisible. The only way to get it back is to re-read the current netlist, and then it shows up again. Just to be sure, I upgraded to the latest test version, but it still happens.
I am not sure that I am doing anything different when this happens. I think it may occur after I have placed a track, and then right-click to end the tool. But it catches me by surprise, and after clicking away on the hide/show etc, I can't always recall the last action!
Version: 4.0.0-rc1-stable release build
wxWidgets: Version 3.0.2 (debug,wchar_t,compiler with C++ ABI 1009,GCC 5.2.0,wx containers,compatible with 2.8)
Platform: Windows 7 (build 7601, Service Pack 1), 64-bit edition, 64 bit, Little endian, wxMSW
Boost version: 1.57.0