We have been working very closely with 3Dconnexion to figure out why people see “run out of application memory” issues or lockups while using their Space Mouse on their Mac (macbook pro, imac, mac pro). It’s a fantastic device, but the included extension has been causing memory leaks on some people’s OSX machines.
While they work on updating that extension, you might try this, since it has helped some users. Upgrade your Mac to Mojave, download and install the latest version of SketchUp Pro, and install the latest 3Dconnexion software.
If that helps you (or not), please let us know here.