Replacing CPE before testing signal levels at the tap or ground block is the most efficient way of systematic trouble shooting

When inspecting a fiber optic connector it is safe to look into the connector as long as it is disconnected from the modem

Which frequency band offers the longest range but slower max speeds?

You are on a trouble call for tiling and pixelation. Your meter shows good downstream level, however the MER/SNR drops significantly on high frequencies. What is the likely cause?