Circle+Radius command often auto-sizes the radius to 1 unit.
When using the mouse, if 'Circle+Radius' is selected, the prompt 'Specify circle centre' is displayed, but if a point is selected Librecad draws a circle of radius 1 and displays 'Specify circle centre' again.
Sometimes similar behaviour happens when drawing a line segment between two points, but I haven't seen anything similar with any other commands (although I haven't been using LibreCad for very long).
If the command-line is used, the command completes successfully.
This happens with quite a few different versions, but particularly 2.1.3 in Windows 10, and 2.1.2 in Ubuntu.