When we skip a software update either for one of our devices or the operating system itself, we always tend to believe that have improved and perfected the previous version to include new features or provide more overall stability.
Unfortunately this is not always entirely true and although initially in theory it should be so, sometimes it only makes the situation worse and more problems are added than we had before, that is, one bug is fixed and three are added.
In this particular case we refer to the last firmware version 7.6.3 released by Apple for the "old" Airport and Time Capsule bases, this update caused connection cuts and made IPv6 tunneling not work and until then gave no problems even if Apple rushed in come up with a solution for this and not entirely satisfactory.
If you belong to the group of users who updated to version 7.6.3 at the time and you are having problems but you don't know how downgrade To download a previous version, here is a very simple solution to carry out the task. We will simply have to open the Airport utility in Utilities> Airport Utility and click on our Airport base in which we want to make said downgrade.
The next step is to click on the version section in the drop-down menu that will appear, but with Alt key or option pressed By doing so, in this way we will activate the field to choose a previous firmware or look for a different one than the one that appears through the Finder.
Once the version is chosen, we will let it install (it takes a couple of minutes to complete the process) and we will have the router ready again so that it works again as before. As you can see, the process is stupidly simple but really effective.
More information - Airport utility comes to version 6.3