Download speed consistently dropping to 20mbps and under whilst upload speed remains 115mbps

I've been having issues with my internet service for pretty much 10 months at this point (since I got it). I'm running an Arris S33 Surfboard and notice frequent drops from normal gigabit download speeds to <20mbps. When these drops occur, whatever I'm doing experiences a massive burst of packet loss which frequently leads to a complete disconnect or if I'm lucky a like 20 second lag out. Whenever these drops happen, it's caused by event codes 16 or 20 and recovers with event codes 22 or 24. However the timeframe between the drop and recovery varies greatly (sometimes <15 min, sometimes over an hour). all of the event codes pertain to the OFDM PLC channel 160 on the modem. I've looked through the power levels and snr of all the channels and all of the downstream channels are hovering within 0-5 dBmV for power and the SNR for most channels is 40-43dB (OFDM PLC channel 160 at 41dB currently) and a few channels at 37dB. However, I have also seen the OFDM channel at 0dB on multiple occasions but am not sure whether that is a bug or not. upload power is 43-44dBmV on all channels except the OFDMA channel which is at 38dBmV. I've had techs out on multiple occasions, one who completely replaced the RG59 coax with a new RG6 cable and another set of techs did maintenance on the apartment junction box but none of this has fixed the issue. Lastly, as a side detail, the upload speed is almost never touched by these issues and maintains a frequent 100-115mbps. If anyone has had a similar issue and fixed it or knows the cause, I'd appreciate info. Thanks