Wired Apple Keyboard A1234 - numpad keys (1,4,7) no longer working

I have a wired Apple keyboard (Model A1234) and discovered this week that three keys on the numpad (1, 4, 7) no longer work. Every other key works, but these three in a line on the number pad do not.

I am not sure when this problem began, but I believe it is recent as of the past week or so. I am using a 2018 iMac and have tried rebooting and plugging the keyboard into different USB ports. My MacOS version is 10.15.1.

Is there a solution for this? A software patch or something I should try with the keyboard hardware itself? Specs from System Report below:

Apple Keyboard:

Product ID: 0x0220

Vendor ID: 0x05ac (Apple Inc.)

Version: 0.71

Speed: Up to 1.5 Mb/s

Manufacturer: Apple, Inc

Location ID: 0x14420000 / 12

Current Available (mA): 500

Current Required (mA): 20

Extra Operating Current (mA): 0