This occurred, and it was entirely avoidable because the EGT defect was disregarded.
Your EGT is to blame since it would have dumped extra fuel into the dpf to raise its temperature because it believed the dpf was operating too cool for regeneration to take place. The dpf becomes overheated because of this. The white stuff you're seeing is really the result of the dpf physically incinerating the trash it contains when temperatures reach 800 degrees or above. This causes the trash to condense within the filter, which is now the source of your problem.
While egts on gas-powered vehicles are usually not a big deal, on newer diesels, they can cause major problems.