Perhaps the OP is finding some of the "fines" left over from Kubota's machining processes?
Many have noticed metallic residue when draining the front axle,as have I?
Are you sure all the glow plugs are good?
I remember those 2.5mm fabric covered hoses!
Used to keep a meter of it around.
Even used it to repair my 6.5 GMC diesel return lines.
Have yet to hear of this being an issue with Kubota engines.
Good Luck!
While the GR2120 owners love them,the long term maintenance cost will disappoint.
Cables,HST issues,and more.
A smaller bare bones used BX with any deck may be a cost efficient solution.
Good Luck!
Kubota has had tire/wheel combos from WholeGoods(dealer salesman) at reasonable prices.
Anybody checked on them lately?
Used to be at set of 4 BX combos was about $400.
Merry Xmas!