Although it is not a common problem, I have seen it a time or two. Normally the back flame means the burner tube is blocked, often by insects or similar. I carried a long Bristol brush on my service truck that I could insert all the way up in the tube to clear it. Looks scary, but usually does not take much to fix nor should it do damage. Amazing sometimes to see how much can accumulate in the tube.
It is unlikely to be a gas pressure issue as when regulators fail they do so to the low side so pressure drops off. Are your other gas appliances working? For example, is the flame on your cooktop burners normal? If the pressure were too high the flame will actually lift off the burners.
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC