Interesting the OMD EM1 does seem prone to functions turning on and off with different settings.
Turned the first noise filter option off in the menu for longer exposure times and now unable to turn it on again so do not expect to be able to necessarily be able to turn settings on and off and on again with this cameras menu even after doing a more comprehensive reset.
Not the end of the world, the next noise filter reduction option for the more common shutter times used is still on and had not intended to use this camera for astro photography.
Have reset functions on the Fn1 button for instance without any problems.

cheers Nick