I got the same issue with SLPlugin.exe using Firestorm x64. 126.96.36.199531, except i don't receive any error message pop-up window. I noticed the issue in my Application Events Viewer in Computer management on Windows 10. " Faulting application name: SLPlugin.exe, version: 0.0.0.0, time stamp: 0x60f86a77
Faulting module name: libcef.dll_unloaded, version: 188.8.131.52, time stamp: 0x5eac9798"
Now I agree with some others comments here, it's possibly related with Chromium Embedded Framework (CEF), some kind of dynamic library issue. Also some issues are often related with CEF and dullahan_host, but issues with dullahan_host can make Firestorm crashed by itself (randomly).
So this is my experience right now with SLPlugin.exe, but as I said it doesn't appear to create any issue in my Firestorm, only a red flag error in my Windows 10 Events viewer !