Saved blocks not able to be inserted into a new drawing

I'm new to libreCAD (LC), but not a total newb to drawing packages, having used MS Visio for a long time.

I'm running the latest LC version, 2.2.0.2-1build3, available on Ubuntu 24.10

I created a simple building plan, created some blocks which inserted without issue into the drawing. I saved the blocks in my home directory. LC knows where they are and they show up in the Library Browser.

However, I've created a new drawing and the blocks wont insert. When selected, I only get the vertical and horizontal cursors, without the rectangle showing the overall dimensions of the block.

This looks like a bug, although it's not beyond the realms of possibility that I'm overlooking something. Any suggestions would be appreciated.