[MlMt] MailMate update denied

[David Ledger]

I am currently up to date with “Normal Releases” according to the 
Software Update panel of Preferences, but whenever I start up MailMate 
(which is rare because I keep it and the laptop running) I get a popup 
saying:
v v v v
MailMate is running on a read-only file system and can therefore not be 
updated.

If you downloaded MailMate from the internet then moving it out of the 
Downloads folder should solve the problem.
^ ^ ^ ^

The system is a Mid 2011 11” MacBook Air running High Sierra 10.13.6. 
The filesystem is APFS with the base drive having one container 
“Container disk1” that contains one Volume “Macintosh HD”. It 
has no read-only volumes.

Has anyone else seen this?

David