Solved! Go to Solution.
If a FIOS tech is on his/her way, let them do their job. I am surprised to see a signal booster placed on the line. Many FIOS installs are too hot and need to be attenuated. This one is just the opposite.
Could be a splitter, or the quality of the cable and/or connectors. Post the results after the tech leaves. If you still have an issue, I am sure you will get many constructive suggestions.