Maybe there was a batch with different wifi hardware, but I have an older and newer one (newer one came with a bit different mounting bracket) and both seem fine.
If the firmware doesn’t fix it, try different 2.4ghz wireless channels, but sometimes interference can be so bad it affects every channel. Maybe your neighbor is teleporting a couple times a day or something 
When my distant one with bad signal disconnects it does seem to take a while to reconnect (the disconnect is usually due to my router booting it due to hitting the -75db threshold I have set). So maybe the fix is just to speed that reconnect up, not sure if it will help with disconnects, but maybe.