I've found that with the current (Drupal 8) version of Pathauto, it is not possible to have both custom and automatically generated aliases per translation - only per node. For example, if I have a node translated into French and Spanish, and I have automatic aliases, and set a custom alias on the French translation, that custom alias will override the aliases for the Spanish and English translations of the node, as well.
This patch takes the langcode into account, as well as the entity ID. I've tested it pretty thoroughly, but I've never gotten into the guts of Pathauto before, so please test and let me know if anything is missing. It now allows for each translation of a node to use either the custom or automatic alias.
Needs work
1.0
I18n stuff
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
The latest patch did not apply on Pathauto version 8.x-1.11. I re-rolled the latest patch and made it compatible with 8.x-1.11.