Delve treasure (almost) reduced to zero

Xbox Series X

Delve treasure has disappeared
What you were expecting to happen, and what actually happened:
Went into level up the delve hoard, went to use rings etc. Some of these I had hundreds of, now I have single figures.

How often does
this happen? When did it begin happening?

Noticed this today

Steps to make it happen again
Assuming this is a one-off?

Did you ascend? if so, some may have been sacrificed.