iodéOS 6 has WiFi problems on the Sony XA2, and these issues slipped through beta testing and wound up getting rolled out OTA (over the air) to many people’s devices. The upgrade was quickly removed so not all but a few people did the upgrade and are facing the issue. We are deeply sorry about this, and will do all we can to remediate and prevent these issues from reoccurring. As @ AlphaElwedritsch pointed out, the way Android Open Source Project is structured prevents downgrades - reverts to a previous release - for security reasons. A downgrade attack would allow reopening security exploits that were fixed in current versions.
We could not find a quick fix, which means that people with these devices must flash their device to factory image and manually downgrade or send their devices back to us if they bought them from the iodé store. Here at iodé we want to be transparent about such errors on our part and use them as opportunities for improvement, and mitigate their recurrence. We are looking into measures we can take on to prevent these kinds of mistakes in the future.