I hope someone on here can steer me in the right direction. Unit is fairly new 4 years maybe 5 tons ran through. This year I have been noticing this said thump as seen/heard in attached video. It was thoroughly cleaned early this season and has only ran maybe 12 bags so far. The operation is fine just this random thump through the cycle. I have watched and there is no rhyme or reason at all when it occurs ie feed or combustion. When the stove is on the down cycle it does not do it only on the ramp up, mid and way down (running in auto mode). Before I start chasing my tail any ideas or suggestions? Really appreciate any and all help!