This is a solution if you are having trouble unlocking a collectible-type achievement that the game thinks is completed.
I completed the entire game (including DLCs and got all achievements) and had one achievement glitch on me at 95% (Explorer - 20 Sightseeing locations) in the achievements app. The game menu of Sunset Overdrive said I had all 20/20. I tried to go back and get all of the locations again in one sitting and it still did not pop the achievement. I uninstalled and re-installed and that did not work either. Lastly, I waited a few weeks, no pop.
The issue if you have a collectible-type achievement glitch in this game is the fact that it uses Cloud Saves and does not allow you to use manual saves. So when you load up the game, it loads the save from the cloud without asking and makes it difficult to bypass....but not impossible!
The only way to get a collectible achievement to pop is for it to pop on the that final collectible. And the only way to go back and get that to happen again is to start a new game, unfortunately. Once I was done with all the other achievements, I attempted to bypass the cloud save sync that happens right after you press
on the main menu screen. Note: I was originally playing on an Xbox One X and I could not get the game to not sync...I tried going offline but it told me I needed to be "online" to play but this is because the Xbox One X was not my Home Xbox...
So I downloaded Sunset Overdrive onto my Home Xbox which happens to be an Original Xbox One with the plan to not sync the cloud save (by possibly going offline) and start a new game, progress the story to after I unlock amps, then visit all the sightseeing locations again in one sitting. I booted up the game online and was able to cancel out the cloud save sync first try (Press
on the main menu, save sync pops up that you need to [quickly] press
to cancel then scroll right once
and press
to select Stop Sync). Note: I assume the Go Offline method would have worked the same but I did not have to go that route.
This took me to a new game where I selected whatever options they offered to get into the game as quickly as possible and then I got to the part of the story where I defended the first defense zone and received amps (prior to this, the sightseeing locations were not available on the map). I then used a guide map to find all locations as efficiently as possible. Once I popped the achievement, I closed the game, went into the save options and deleted the local save from the console. When I booted up the game again, it automatically downloaded my completed game save from the cloud which still had everything collected and completed!
Hope this helps someone out there if you had any issues!