[Already reported by email but not had a response yet]
New theme controls introduced in RW8 (e.g. sliders and number boxes) are unresponsive for me on 10.13.5. This bug can be replicated in the new themes shipped with RW8 and third party ones. RW preview refreshes but changes to theme settings never take effect and are stuck on the defaults. The issue occurs in both the Master Style and in the Page Inspector.
Example -> Engineer theme --> Increase font size to 26px - it remains stuck at 18px. 
I reverted back to RW 8.0.3 and all is working fine again.