Not sure how emissions laws apply to off road machinery compared to cars. The legal response for a car is to buy and install a new DPF.
If it were my machine, I would remove/gut the DPF so it didn't cause trouble again. Its obvious that Kubota is identical to Ford/GM/Dodge and others which have implemented these DPF setups, but they get clogged under normal use and make the machine inoperable without throwing significant money at them.
