There are a couple of bugs that effect the ECHOS, but none of them permanently prevent collecting all of them. First and foremost, Make sure that each ECHO is collected, and not just viewed. Mission-based ECHOs can be especially troublesome with this. Also be aware that ECHOs do not always mark off on the map, and that Some ECHOs will not appear straight away.
Viewing does not collect an ECHO
While not a bug, this is something that needs to be especially pointed at. Once you start viewing an ECHO, another interaction should appear to collect it. If you view the ECHO, but do not collect it, it will not count towards activating the ECHO for the achievement. Furthermore, there is suggestion that this might contribute towards ECHOs being buggy.
ECHOs found during missions and side-missions
ECHOs that are tied to a mission are especially buggy, and will likely cause problems, when you try to collect them. These include ECHOs discovered during a mission, such as the ECHO of the Cleaners making napalm, or an ECHO that acts as a mission objective, such as the ECHOs used to track down missing persons.
If you can not collect a mission ECHO during the mission, there are several solutions you can try:
- Come back for the ECHO after you complete the mission: Some ECHOs don't seem to like being collected during the actual mission where you are expected to discover them. At least half of the buggy mission ECHOs, in my game, were resolved by simply coming back outside of the actual mission.
- Access the ECHO area from an alternate direction: I found that some ECHOs appeared easier to collect if accessed from a different direction. When you view an ECHO, the included area will be coloured in, both in game and on the mini-map. On occasion, you will notice an alternate entry into the ECHO area than the direction have already come. On rare occasion, when the other solutions did not seem to work, I found that coming into the ECHO area from a completely different direction or entry point seemed to unlock the ECHO for collection. I especially noticed this solution for the ECHOs tracked during the side-mission Missing Persons: Noble Squad.
- Collect the ECHO in another players game: The highest-voted achievement solution on TrueAchievements suggests that you might have more luck joining another players game to access the same mission, without the buggy ECHO. This is a lot easier for main missions, where match-making is available, but you can also replay side-missions if you are playing with a user who has not completed it. I found this solution doing some background checking, and can not confirm if it is an easier or viable solution.
ECHOs that appear collected, but still show up on the world map.
This one had me for a while. Some ECHOs will not register as collected, for the purpose of displaying collectibles on the world map. A good example of this is the ECHO "General: 6 - Cleaners". These ECHOs will still be collected, and count as collected for the achievement.
If you run into an ECHO that appears to linger after collection, you can access your collected ECHOs through Menu > Intel > Field Data > ECHOs. If the ECHO actually appears, in this location, with an image of it and a description of the activity that took place, the ECHO has been registered as collected.
ECHOs that do not appear, outright
Not as much a bug, but some players appear to have concerns with ECHOs that do not appear, at all. It should be noted that some ECHOs are tied to missions and mission completion, and will not appear until the prerequisites are met.
A good example of these are the Missing Person ECHOs, which only appear once the player starts the respective side-missions. There is also an ECHO, "Rogue Agents: 6 - Invitation", that only appears once you have completed all of the main missions.