This issue is a follow-up of
EZP-27011, and the respective patchj i sneeded to reproduce the current issue, since there was one scenario where the "main_location_priority_i" was not being updated. This was happening the first time the priority was being updated.
-Created one article with priority=0 (the default)
-Search solr. I have "main_location_priority_i": 0, - Correct
-Update priority to "1" - First update
-Search solr. I still have "main_location_priority_i": 0, - Incorrect
-Update priority to "2" - Second update
-Search solr. I have "main_location_priority_i": 2, - Now it's Correct .
After this point, each priority update is reflected in sorl search correctly. Only the first update wasn't reflected.