[thimk]

and has been doing so ever since kodi 16.

Start-up is snappy 1-2-3 and we're ready, but closing, no. 

previous machine OSX 9,5 MBP 13" (early 2010) 16GB RAMpresent machine OSX 9.5, MBP 17" (late 2011)  16GB RAM

[Klojum]

To receive meaningful assistance you will need to provide a full debug log.

The instructions are here... debug log (wiki)

If you are using the Basic Method, then ensure the following is applied...
1.Enable debugging in Settings>System Settings>Logging,
2.Restart Kodi
3.Replicate the problem.

If you are using the Advanced Method ensure you have correctly created and applied the advancedsettings.xml file.

In both instances, you should see the word DEBUG throughout the log.

Note: Full logs only. No partial or redacted logs
Do NOT post your logs directly into the forum. Always use a paste site like pastebin.com. Post the link to your pasted log in the forum