I'm not doubting you but that seems hard to believe because the flame guide is fairly heavy compaired to the pellets and I just can't see how it would be pushed off the burn pot. Try sealing it in place with some high temp silicone.

One thing to check, is it the correct flame guide? Looking on the Harman Web site I found the part number is 3-00-08534. The part # should be cast right into the part.

Also, did you have any maintenance done to the stove since this is happening and what fuel type are you burning?

are you installing it right? it should never fall out since you need to slide it up before you can remove it

I have the same issue. Just started this season. YES I placed it far back, cleaned it all and yes it gets pushed out by the pellets. I don't care how heavy you think it is. It makes the stove burn wrong and causes smoke to come out if not stopped and fixed. I am afraid to leave my house with it...which is raising my fuel bill. I also called the people who put my stove in and they said I was crazy. I really need it fixed! Thanks for all help!

check for a buildup of clinkers [hard deposits] in the burn pot . that can make pellets push up and move a flame guide also be sure no crust build up on the sides of the burn pot that the flame guide sits on or on the bottom of the flame guide. clinker build up can also slow down your ignition