Hey @lleachii, sorry to hear you are having issues.
I just tested r6646 on my MX60 and am unable to reproduce the LAN port issue you are seeing.
In my screenshot, LAN1 is actually plugged into a 100mb device, so that is expected.
Just to confirm, did you do a factory reset after flashing r6687? I recommend trying that to start. We also recently had a fix merged into master at https://github.com/openwrt/openwrt/commit/c61c709f4e3f4331716d6e5624f7678d03b5d80c to fix cases where the switch would not work after the change to the 4.14 kernel.