I just right this very moment received a DC505A. And guess what,
It displays the exact same behavior!!!! Only one digit randomly comes up when inside the TM506,
but all are present when connected to the extender!
To me, that doesn’t make any sense, unless, on each and every slot, somehow the plugin makes a deeper contact inside the slot, that the actual plugin is incapable of making... But even that assumption is flawed.