Disk Utility Fails When Partitioning

Hardware: MacBook Pro 2017 16GB RAM etc

OS: macOS 10.13.3

Disk Utility seems pretty permanently broken for me. Whenever I try to partition an external drive, it always fails. This is true for false drives, external hard disks etc. It's true for "factory fresh" media and any other media (connected via USB directly to MBP using Apple USB-C to USB-A adapter).

All I'm attempting to do is take a brand-new hard disk (formatted for FAT32 as usual for such devices) with an existing GUID partition table, and replace it with a single HPFS encrypted partition...

Attempt 1:

-- Mount volume, select Partition button in Disk Utility.

-- Name there partition, choose "Mac OS Extended (Journaled, Encrypted)" as format.

-- Enter encryption password, click Choose

-- Click Apply, then Partition to begin the process

Result: Operation fails immediately with "Invalid arguments"

Attempt 2:

-- (repeat above steps)

Result: Operatin fails immediately with "MediaKit reports not enough space on device for requested operation"

This is stupid .. I'm formatting the ENTIRE PHYSICAL VOLUME (4TB). How can there not be enough space?

Any idea?

--Tim

P.S. I'm glad Apple is reportedly focusing on bug fixes in the next OS release if this is anything to go by. Disk utility used to work nicely, and in making it "easier to use" Apple seems to have pretty much borked it.