I can confirm the fix from Andras works. The SlicerLauncherSettings.ini file is in the bin directory and in addition to adding the line 12\path=<APPLAUNCHER_DIR>/bin/Lib/site-packages you need to increment the last line of the section to size=12.
Other notes: the nightly crashes when started over remote desktop but the 4.8.1 release does not (probably the OpenGL2 issue) and I see the same slowdown in Slice rendering that Andras reported.