Wifi antenna are at the base of the unit. If sitting on its side or upside down the device’s wifi RSSI, Quality and TX Rate improve significantly. Noting the ventilation design, can the device be used in alternate orientations?
Can you provide us some details on the device, such as make and model number? Difficult to make a recommendation without knowing exactly what device you are referring to.
Taking a stab in the dark here, but if the WiFi antenna(s) are removable you’ll probably get more improvement from replacing the antennas with something that has an extension cord and higher dB gain vs re-orienting the device. Something like this maybe…
What AP / NIC are you using?
Signals propagate from the antenna in the form of waves, if the waves are synchronized, things work best. If they are at odd angles, things don’t work best.
The only time you need to angle your antenna is when you are trying to aim toward devices which are on different elevations. Think of it like waving your hand at someone. If you hold up your hand and wave it, they see it better if you hold it straight up. But if you held your hand flat toward the ground, and just moved it left and right, that would be harder to see than if you just held it straight up.