@Nachti
DavidW, the author of SCS, seemingly fixed this bug in SCS 33.4.
Readme from latest version of SCS still states:
aTweaks
aTweaks was designed to function with SCS, but is now quite out of date (and not currently maintained). It is designed to be installed after SCS. (This is an exception to the usual rule that SCS should be installed last.) At the moment I'm fairly sure its Fiend components are at least partially incompatible with SCS Smarter Mages and Improved Fiends; to be safe, use one or the other. Its other components are probably compatible with SCS.
i.e. Use at your own risk. Nothing in the readme about any sort of fix addressing aTweaks Fiends components.