This may or may not work for some people, but I'm finding it works for me...
When my CDJs freeze, I hold the track search back button and backspin the jog wheel very slightly until the screen goes black.
As soon as the "Now Loading" message appears, press and hold the track search back button again for 15-20 secs.
"Link Access Error" message should display and the track re-loaded.
If the large waveform doesn't show, hit track search back and immediately hit track search forward to show the waveform.
This saves disabling the Link or taking out the LAN cables or even switching off the units.
I can't get this method to work when the CDJs freeze on hot cues though, sadly - any suggestions for this welcome.