HP-25 Co-luminous segments

[Tom Flatterhand]

My HP-25 recently purchased on an auction platform appears to be in good shape. However, it exhibits a phenomenon: when I press the keys on the middle row of the keyboard, all of the upper segments, except for the fourth, of the 7-segment digits light up dimly in the display. My meager electronics knowledge suggests that one of the keyboard's matrix wires (if it works that way) has a weak short to another wire. Do any of you have a concrete idea what this could be and if this quirk can be fixed?