Reports of Joy-Con connectivity issues continue to gaming forums and it seems the workarounds given by Nintendo have not appeased consumers. Most reports have commonly pointed out that the left controller usually looses its connection with the console. A YouTube user named Spawn Wave has apparently discovered that the rampant problem might be due to a manufacturing design of the left unit, which causes its sync issues with the Nintendo Switch.
His video showcases a teardown of the two controllers and indicates the subtle differences behind their design. He notes that the right unit features an external antenna, whereas the left unit relies on a built-in model on its motherboard. Game Rant reports that an integrated antenna assembly is most likely to have connectivity issues compared to an external model. It was also speculated that the left unit's antenna might be in contact with the analog stick's metal plate, which might add to its erratic behavior.
Spawn Wave has also suggested that it might be possible to add an external antenna to the left Joy-Con to fix its sync issues. The modification supposedly involves an extra wire and some small tinkering to effectively increase its working range. A twitter post from the YouTube user reportedly confirmed his speculations. He claims that the problematic unit now outperforms the right Joy-Con thanks to his modifications.
It seems that the manufacturer might have overlooked this issue with the controller final design. An article from Gamenguide recently detailed the problems with left unit. Nintendo supposedly acknowledged the issue and instructed users to download the day one patch to hopefully fix it. However, it seems that only a handful of users saw improvements while the rest continued to get disconnected. The company even went as far as instructing consumers to turn off their wireless devices, which is obviously a hassle for gamers.
Nintendo has not yet officially commented about the recent finding shared by Spawn Wave. If the left Joy-Con is indeed problematic with its sync issues and it is confirmed to have a manufacturing defect. A product recall situation might be a possibility and could cost the company a substantial amount to offer replacements.