Sidebar issue (right side)

I have only recently developed an issue whereby the right sidebar defaults to maximum width when Properties is selected. The sizing icon is ineffective with properties selected. Selecting another function, Layers for instance, the sidebar remains at maximum width, but the sizing icon is effective and the bar can be narrowed. The narrowed format remains until Properties is selected again and the problem reemerges. Closing and opening the file again does not fix the problem.
The problem first occurred with a file that contained a number of linked block instances. Now it occurs whenever Rhino is opened.
OS 10.14.6.
Version 5.5.5 (5F96).

Hi,

Try resetting your plist preferences file for Rhino 5.5.5 for Mac. See https://wiki.mcneel.com/rhino/mac/resetprefs, you can also save a copy of the current plist in case you want to restore it.