Cannot partition all free space

[madgick]

I have about 200GB free space, but when I try to partition using Disk Utility, it will only let me use about 51GB of that space:

As you can see, my little slice of pie wont extend further into the 448GB area, even though in the bottom right it says only 311.13GB is being used

Any ideas what could be going wrong?

 

[organicCPU]

Can you click on Untitled and press the minus sign?

 

[nudoru]

I have this same issue, but I can't create a new partition larger than 28gb. Did you solve it?
[doublepost=1527599942][/doublepost]Found the solution!

Local time machine backups are causing it. You need to turn them off and delete all local snapshots. After that, you'll be able to resize it and create a new partition. Be sure to turn TM back on afterwards.

Refer to this
https://www.imore.com/getting-apfs-resizing-errors-using-disk-utility-fix-may-help

That deleted all but 1 snapshot for me, I had to remove the last one manually using the solution here
https://forums.macrumors.com/thread...machine-local-backups-on-high-sierra.2073998/