At a rough guess I would say that the ASX has concerns with...

At a rough guess
I would say that the ASX has concerns with transparency of NIU's operations and the corporate governance along with control measurements of grades,
as TL's rough system/procedures are not based on precise sampling.
DT is offering imprecise theories of more gold at depth!

I believe the ASX see risk around the current mining and processing of operations
with a strong leaning currently towards grade managed control/sampling protocol.

So it appears we have an extremely high risk management issue in mining operations on results of sampling which is creating distribution of much uncertainty for mr market in the ASX's eyes.

FID