I've been struggling a lot with Drush 9 sql:sync the past few months. I've gotten it to work a few times, but I've been stumped by this most recent problem:
$ drush sql:sync @prodv2 @local --debug
Using the Drush script found at /Applications/MAMP/htdocs/ianmoffitt/vendor/drush/drush/drush using proc_open
[preflight] Config paths: /Applications/MAMP/htdocs/ianmoffitt/vendor/drush/drush/drush.yml,/Applications/MAMP/htdocs/ianmoffitt/drush/drush.yml
[preflight] Alias paths: /Applications/MAMP/htdocs/ianmoffitt/web/drush/sites,/Applications/MAMP/htdocs/ianmoffitt/drush/sites
[preflight] Commandfile search paths: /Applications/MAMP/htdocs/ianmoffitt/vendor/drush/drush/src,/Applications/MAMP/htdocs/ianmoffitt/drush
[bootstrap] Bootstrap to none [0.13 sec, 8.14 MB]
[bootstrap] Drush bootstrap phase 0 [0.13 sec, 8.14 MB]
[bootstrap] Try to validate bootstrap phase 0 [0.13 sec, 8.14 MB]
[error] The "destination" argument does not exist. [0.13 sec, 8.19 MB]
Can't find anything online towards this specific error message. Not sure what I'm missing or what to even check.
Again, this command worked about a week or so ago. All I've done since then is run composer update. Did something change recently?
Using Drush 9.3.0.