That's a beautiful crush. Better than I can do at home. I doubt that's the issue.
Are you using enough water? These systems have a lot of dead space, so upping water:grist ratio is needed. I use 1.5+ qt/lb, typically closer to 1.8. (edit: can be lower for big beers; there's actually a fixed dead space at bottom, and variable around the malt pipe.)
Also, I find a setting for the pump that doesn't overflow and just stick with it. Idk of it could be opened more later in mash.
Ha! That’s interesting, thanks. I was close to going down the road of milling my own grain.
Regarding water:grist, that’s something I forgot to mention, so thanks for suggesting, I’ve tried varying levels from 3litres/kg to full volume with no sparge.
On occasion i’ve left the pump on the absolute minimum recirc throughout the full 60 min mash and it seems to have gotten through it with no blockages, though the point of this system is to get a reasonable flow to keep mash temps good and efficiency good too.