Pool filling up own its own

Hi,

I have 10x3tb drives in raid z2.

I have been using FreeNas for years.
Today i upgraded to TrueNas and now space keeps vanishing from my pool.
I had around 2tb free at the start of the day now i have less than 200gb.

Looking at zfs the difference between Main and the sum of everything else i seem to be missing 1.6tb.
Any idea on whats taking up this space?

A critical alert has also appeared after the upgrade (I have ordered a new 3tb drive to replace this one).
Does this have...

Pool filling up own its own