I never see this problem when I first start a game - it takes a while to show up. I usually first notice this bug during one of those "open crate, mob appears" missions around the time I have L2-3 with at least two corps. I'll try to fire weapons while reversing and game will refuse to do both at same time. Usually saving and reloading will fix it but not always. I'm attaching a save where the foes were about to come at me and I couldn't back up, but after reloading it a second time it did let me fire while reversing.