What kind of channels are you watching? Analog or QAM/Cable Card/digital? Are the issues recorded, ie. you can rewind and watch the breakup again (that would rule out any HDMI or TV issues).

If you're using digital cable, then it's likely a strength issue. Did the guy measure the signal *after* the splitter and new runs? An 8-way splitter will lose about 11db right off the bat, and if he didn't touch the line in question, we don't know what quality it is - it could be old RG59 with bad shielding.

You might want to try moving the box to another line to see if it improves, or connecting it before the splitter.