When configured in Up/Down mode (to control a volume using two momentary type buttons) the GPI connections are reversed. On the GPI control panel the first pin is shown to be decrement and the second as increment but the actual operation is the reverse.
There is a mismatch between the indication on the control panel and the actual operation.
ESP-88 (v1.241 or later, CS Designer (v1.241 or later)
To workaround simply reverse the GPI connections so that the operation is correct and ignore the indication in the GPI control panel.
Issue resolved - Designer (v3.043 or later), ESP-88/00 (v3.040 or later)