BCD4511 Seven Segment Display Decoder + Diode Matrix
I don't see any load resistors from the 4511 to the display - you need these to limit the current to the display elements.

For a 12V supply try a value in the 1K ohm range to limit to about 10mA per segment. If brightness is an issue you could try as low as 500 ohm for 20mA. I wouldn't go much lower than that.

The resistors should be at least 1/4W and preferably 1/2 W size to ensure they won't burn up (they will shed heat instead of in the 4511 and the display.)

More: a handy way to encode the switches in a single chip: https://www.onsemi.com/pub/Collateral/MC14532B-D.PDF This should make your board simpler - no more diodes. Yeah, SOIC, I know - use an SOIC to DIP adapter like this one: https://www.digikey.com/products/en?mpart=PA0006&amp;v=315