For VFB forms the "Billing Address" label/legend vertically in iOS Safari.

The CSS workaround can look like the following but may need to be tweaked for individual forms. Enter this CSS in the Custom Styles box when in a VFB form:

.givewp-groups.givewp-groups-billingAddress.givewp-groups-billingAddress-billingAddress fieldset legend,

.givewp-groups-billingAddress fieldset {

display: block!important;

}