Strange light issue

[SirJanin]

Hello, we are having a strange issue with our 2007 Yaris hatchback. If we switch on the dash board lights (when driving at night) both tail lights go out. Turn the dash lights off and the come back on. So now when driving at night (which we avoid) we have no dash lights what so ever. I checked all the fuses and they seem fine (not sure if its a fuse issues due to the fact that they work, just not together). Has anyone heard of this happening or have any idea what may be going on? Thanks