Firefox on macOS Delete Key Doesn't Work

In most if not all of the fields I type in on macOS the delete key no longer works. For example go to add a food item start typing in the search bar and then hit the delete key. Rather than backspacing nothing happens. I'm testing this under FireFox 66 on macOS 10.14.4. This is not a problem under FireFox 66 on Linux Mint 19 or under Safari under macOS. To attempt to correct this I've totally flushed all browser history data and attempted again. I've also disabled all plugins to make sure that they weren't creating the problem. This isn't a problem in other sites running in the same browser in a different tab.

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