6.12.4 - data loss and unraid crash while moving data on zfs drive within same dataset/folder

I 1st observed this while moving some data around on one of my disks.
- 4 disk array (1x parity, 3x data).

I observe this behaviour on the drive with zfs file system.

Running the following command I moved multiple copies of a Windows10.iso file one folder up.

I can see that RAM is filling up:

Unraid GUI only shows read activity on the disk3 and NO writes.

Unitl I get this:

The moved files are lost!
3 out of 5 files were moved and nothing can be found in the target folder.

And Unraid UI is crashing due to lack of free RAM.

Any ideas?
I know that zfs is using RAM to buffer file transfer, but this does not make any sense.

I lost an unknown number of files due to this issue...
Luckily, I just moved between servers and the old one still holds a copy ....