Download speed issue

I have the 300 / 25 speed tier ( at my home address ) and over the past week or so I have been having horrible download speeds, upload speed is fine.  Looking at the status page on my Arris SB190 I noticed that channel 16 is alternating between locked and not locked with what I'll refer to as a "metric sh*t ton" of corrected and uncorrected errors.  When locked, the SNR is usually around 25 - 27 dB which is well below the 38-40 dB which the other channels are at.  Channel 17 is in the 33 dB range and is reporting a larger number of errors than the other channels.  Power cycling the modem does not change the status, also tried having a reset signal sent from the head end.  No change.

Power level on ch 16 is 3.70 dBmV which is right in line with all the others.  I live in a condominium complex and I have yet to crack open the junction box behind the building to look for loose connections ( it's usually not even closed ).  Would this indicate a wiring issue on premises or in the line somewhere ?  I have had business service at this address for several years and have never had an issue like this with the service.  I'd rather not be forced to take time off work to wait for a technician if this might be something that could be tested from outside my unit / building.  Any suggestions are appreciated.  I do plan on calling in but figured I check here first.

**EDIT**  Forgot to mention that my download speed test results from multiple server locations in different states ranges from 5 to 15 Mbps down when normally it's around 350 Mbps.