Local Clock differs too much from received time

What's the meaning of this ?

This warning means that Smode is resynchronizing to the incoming TC. If it happens only once at the TC startup, it's simply a sign that Smode is correctly tuning to the TC and therefore no problem.
If it happens in the middle of the playback, then it's a bit more worrying, the main risk being to have graphic jumps, linked to the time resynchronization.
Try to increase the level of the signal to avoid those kind of problem.