The left joy-con periodically de-syncing after moving past 6ft issue
is actually a hardware issue not a software one.
the problem is due to nintendo cheaping out during manufacturing.
they should have installed a 2" copper wire antenna but they didn't.
The antenna built in is just a small circuit board copper trace which is installed behind the L button.
I found a video on youtube and i soldered in a wire to the pre existing solder point on the circuit board.
i took the wire from an old ethernet cable i had lying around.
the left joy-con worked great afterwards.
here's the video i found video in case any of you want to fix your left joy con.
... https://gbatemp.net/threads/nintendo-fixed-joy-con-connection-issue-with-just-a-foam.465343/