Sync light flashing is a sign of incorrect signal levels.
You could check on
http://192.168.100.1 (root/root for user/pass).
If its higher than 15dbVm or lower than -15dbVm then there are issues, and a technician will be needed. A high signal level can be fixed by a homebrew method, but since thats in violation of the ToS, I cant tell you.
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Its Lsproc if you cant tell
And I have memorised signal levels, arent I sad