Hey PacketMonkey,
Thank you for getting back with the additional information. I wasn’t aware that you were using two translucent materials. Now that I know this I can say what you are seeing is expected behavior, the engine determines sort priority for translucent materials by checking the origin of the object’s bounds. The one that is closer get’s drawn on top, so think of it this way. Which ever object’s origin is closer is on top.
You can manually set the sort or by selecting a mesh and in the rendering section look for “translucency sort priority” the higher number gets drawn on top.
Aside from that you are running into a classic sorting issue that many devs have to workaround regarding translucency.