As the UI is Scaled up due to playing a higher, but custom resolution, you maybe could try to fix it. You may have already looked into it at some point, but I still like to make it an official suggestion.
The highest playable 4:3 resolution with normal UI Scale is 1280x960, playing on a higher custom res like 1440x1080 causes the UI to scale up and prevents clicking buttons and seeing BFP for example. It would be very nice if there was a workaround since I am not the only one having this problem with custom resolutions.
Best Regards,
Heros5k