Thunderbolt 2 ports not working simultaneously on my MacBook Pro (Retina, 13-inch, Early 2015)

Both of my Thunderbolt 2 ports work, but not at the same time.

Main points of interest:

1. 1. They have worked simultaneously in the past (I've had my HDMI and both Thunderbolt ports connected to external monitors all at once -- worked perfectly)
   2. Each one works without the other (Thunderbolt port A works without Thunderbolt port B, vice versa; both work with and without the HDMI being used)

I am using Mini-Display Port cables to connect the Thunderbolt ports to my external monitors.

Things I have tried:

• • Updating the OS (I am currently on macOS Catalina v10.15.4)
  • Restarting the system
  • Testing each cable individually to make sure it works
  • Testing each port individually to make sure it works

Has anyone else encountered this before? I would rather not have to get charged by Apple to solve this considering the fact that both ports do in fact work separately. Would be very appreciated to have any help.