When setting a size for the switch heights, the defaults are set in rem and comparing it to px is causing a syntax error. So I switched it to use the rem-calc() mixin to resolve the error.
// $switch-bg: #fff;
// We use these to control the switch heights for our default classes
-// $switch-height-tny: 22px;
-// $switch-height-sml: 28px;
-// $switch-height-med: 36px;
-// $switch-height-lrg: 44px;
+// $switch-height-tny: rem-calc(22);
+// $switch-height-sml: rem-calc(28);
+// $switch-height-med: rem-calc(36);
+// $switch-height-lrg: rem-calc(44);
// $switch-bottom-margin: rem-calc(20);
// We use these to control default font sizes for our classes.