Mac w/MS Edge and Basic PAYE Tools won't submit FPS

While doing the manual entry of data and creating payments works, when it comes to submit it fails when using MS Edge. It doesn't, if using, e.g. Safari.

Since Edge was made the default browser on the Mac, couldn't submit anything. Changing back to Safari resolved the issues.

What I'm curious to know is (1) what could be different between the two browsers that make those submissions fail, and (2) how could we force the Basic PAYE Tools to use always Safari, while leaving Edge as the default browser.