The "white" png transparency problem

The problem is that transparent areas of PNG files show up as white in ATEM Software Controller when loaded into Media Player for some users.
Most people don't seem to have this problem. But I do.
I create my graphics in a remote location that isn't connected to the network that my ATEM Switcher is hooked up to, so using the Photoshop plug-in isn't an option for me.
I've searched hi and lo for a solution, but despite there being a fair number of folks who report this, no one has yet offered a definitive answer as to what's causing it, nor has anyone suggested an easy way around it.
However, I have discovered an interesting workaround which makes the PNG files work. I have not seen it mentioned elsewhere:
When I'm creating my transparent graphic in Photoshop, if I add a layer at the very bottom, fill it with black, and then turn the opacity down to 1%, and then save to PNG, the transparency is preserved in ATEM Software Controller (Pre-Multiplied Key is checked under Palettes/Downstream Key).
If I turn the opacity down to 0% on the bottom black layer, the transparent areas revert to white again in the Controller. And if I remove that layer, the transparent areas are also white. Interesting...
Adding a layer of black with 1% opacity is barely visible, if at all. So that's a great, easy solution for me at least.
I'm still curious as to why it happens though...
Most people don't seem to have this problem. But I do.
I create my graphics in a remote location that isn't connected to the network that my ATEM Switcher is hooked up to, so using the Photoshop plug-in isn't an option for me.
I've searched hi and lo for a solution, but despite there being a fair number of folks who report this, no one has yet offered a definitive answer as to what's causing it, nor has anyone suggested an easy way around it.
However, I have discovered an interesting workaround which makes the PNG files work. I have not seen it mentioned elsewhere:
When I'm creating my transparent graphic in Photoshop, if I add a layer at the very bottom, fill it with black, and then turn the opacity down to 1%, and then save to PNG, the transparency is preserved in ATEM Software Controller (Pre-Multiplied Key is checked under Palettes/Downstream Key).
If I turn the opacity down to 0% on the bottom black layer, the transparent areas revert to white again in the Controller. And if I remove that layer, the transparent areas are also white. Interesting...
Adding a layer of black with 1% opacity is barely visible, if at all. So that's a great, easy solution for me at least.
I'm still curious as to why it happens though...