Ok, don't laugh at me for this and no, I'm not just messing with you but I had similar issues with mine, especially, with Retumbo. It's good powder but d*mn do I hate using it! Anyway, like you, it was recommended that I put a piece of straw in the discharge tube and the person that told me about it was very specific that I use a piece of Mc D's straw. So I did, well sort of. A straw is a straw right, so I used the first one I had. It didn't fix sheet and if anything, it made it worse. So after MANY four letter expletives I went and got a straw from Mc D's. Clipped a piece off, screwed it into the discharge tube and gave it a go and I'll be honest, the whole time, I was thinking this is so stupid, it's a freakin straw for gods sake, how much difference can there be. Well, either the big guy up above heard me and took pitty on me or using an actual Mc D's straw was the answer but it made a significant difference. I won't tell you mine runs flawless but it's a rarity that it gives me grief.
So, if you haven't already done so, get yourself a straw from Ronald McDonald and give it a try. Also, if you google it, these things can be programmed to change how fast, slow, etc etc. they discharge a load. Hope you get it sorted out because when they work, they are awesome but when they don't, well, I think you already know the answer to that.