I am staring at a GE First stage turbine blade as I write this. It has dozens of holes in it that channel cooling air through it. The holes are about .25 mm or less in diameter. They are also angled and profiled.
This blade operates in a gas stream that is around 300C hotter than its melting point.
If the cooling system fails due to clogging with molten ash, damage will be immediate, severe and very very expensive.
Please understand that the airlines are currently between a rock and a hard place until they can satisfy themselves that they can fly without wrecking their very expensive equipment.
They can fly, earn revenue, then bust the equipment and lose revenue as well as suffer repair expense, or they can lose revenue until it is determined that there is no hazard, or that the risk is manageable.
At present no one to my knowledge knows enough to satisfy themselves that the risk is manageable. Failure to manage that risk could involve loss of life or grounding a large chunk of the fleet in the coming weeks/months due to lack of engines.