Motorola MB8611 - Internet dropping/reboot - SYNC Timing Synchronization failure and No Ranging Response received - T3 time-out

Solved: I switched to Arris S33 and so far no issues with service or reboots. Still get occasional "RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW. Dynamic Range Window violation" messages in the logs but modem keeps working.

Update: Support has confirmed that this is Motorola software related issue - "In regard to the internet issue, there is a known issue with the specific modem you have, and until the firmware issue from Motorola is addressed, you may experience issues with the service."

I'm having the same SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing / No Ranging Response received - T3 time-out issue as many of the others reported on this forum.

This is very frustrating as my internet drops 3-4 times per day in the same time windows: between 11am and noon, around 3pm, around 6pm and sometimes around 11pm. It's almost like there is a pattern.

Motorola support tells me that this is a cable's provider issue and Xfinity support tells me (after modem is rebooted of course) there is nothing wrong with my line! This is beyond frustration as my work requires fast and stable internet and unfortunately Xfinity is the only provider in the area who has it (fast but not stable!).

My setup:

Cable length: ~130 feet. This consists of 30 feet of underground RG11 from the street box to the box on the side of the house and 100 feet of RG6 from the house box to cable modem (brand new, just replaced). No any connectors or splitters on the line, so this is not a cable issue on my property).
Modem: Motorola MB8611, software version 8611-21.3.7

WiFi router: ASUS AC1900 (RT-AC68U)

Here is the event log after the SYNC Timing Synchronization failure

Connection settings before the failure:

Connection settings after the failure: