I’m experiencing a similar issue: SOLVED: Bug in Slider widget height but only if the Breakpoints are set to “Mobile first”. In that case, base breakpoint (smallest screen) does not respond to changing Slider’s height - it’s stuck at 50vh.
To replicate: set mobile breakpoint as "Base”, Create a Slider (Nestable). Go to Content > Options > Height > Change height > See slider’s height is not changing.