Hi,
Module JA Masthead is working fine with Joomla System Cache.
And it seems there's problem with SH404SEF.
If you turn off
Enable URL optimization
Enable remote configuration
Activate security functions
The module will work normally.
Dev team will try to figure it if there some way to make it compatible with Sh404SEF component.
You could temporary disable the options in Sh404SEF component if you want.