Cable modem drops connection for 5 seconds about every 20 minutes

DOCSIS 3.1 Netgear CM1000 Cable Modem.

I am in Fort Lauderdale Florida.

Connection works great when it is working -- up and down speed is great.

Only problem is that my modem drops the connection for about 5 seconds every 20 minutes approximately.

This happened on my old Arris Surfboard DOCSIS 3.0 and I had hoped that upgrading to the newer DOCSIS 3.1 Netgear CM1000 would help.

It did not help. 

A Comcast technician came out and was unable to solve the problem.

I have a similar or identical problem to this user's forum post:

https://forums.xfinity.com/conversations/your-home-network/internet-drops-for-5-seconds-every-20-minutes/602dadcbc5375f08cdd3aa0d

I posted full info below but the thing that stands out is that I have a lot of critical sync errors along these lines:

SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;

Below is the EVENT LOG information from the CM1000 Cable Modem:

(I am deleting my MAC address from this info).

I have numerous instances of the following critical errors:

SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;

No Ranging Response received - T3 time-out;

Cable Connection info from the modem UI below.

Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency 
669000000
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 669000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 25 669000000 Hz 10.6 dBmV 42.8 dB 3442580866 351 427
2 Locked QAM256 2 525000000 Hz 10.0 dBmV 42.6 dB 3440874604 66 273
3 Locked QAM256 3 531000000 Hz 9.8 dBmV 42.5 dB 3441046675 376 1535
4 Locked QAM256 4 537000000 Hz 10.1 dBmV 42.8 dB 3441184693 1423 5052
5 Locked QAM256 5 543000000 Hz 10.0 dBmV 42.7 dB 3441223314 1430 4783
6 Locked QAM256 6 555000000 Hz 10.2 dBmV 42.6 dB 3441396573 1696 5629
7 Locked QAM256 7 561000000 Hz 9.9 dBmV 42.3 dB 3441165496 1744 6529
8 Locked QAM256 8 567000000 Hz 10.0 dBmV 42.5 dB 3441202217 2760 6362
9 Locked QAM256 9 573000000 Hz 9.9 dBmV 42.6 dB 3441278852 2370 6056
10 Locked QAM256 10 579000000 Hz 10.0 dBmV 42.7 dB 3441436025 1494 5364
11 Locked QAM256 11 585000000 Hz 10.1 dBmV 42.7 dB 3441471948 1314 4976
12 Locked QAM256 12 591000000 Hz 9.9 dBmV 42.6 dB 3441501130 1464 4349
13 Locked QAM256 13 597000000 Hz 9.9 dBmV 42.6 dB 3441520854 2366 5243
14 Locked QAM256 14 603000000 Hz 10.3 dBmV 42.6 dB 3441530755 1274 4548
15 Locked QAM256 15 609000000 Hz 9.8 dBmV 42.3 dB 3441462524 1292 5035
16 Locked QAM256 16 615000000 Hz 10.2 dBmV 42.6 dB 3441581636 1383 5582
17 Locked QAM256 17 621000000 Hz 9.7 dBmV 42.5 dB 3441847863 1492 6067
18 Locked QAM256 18 627000000 Hz 9.9 dBmV 42.4 dB 3441862437 1771 6513
19 Locked QAM256 19 633000000 Hz 9.7 dBmV 42.5 dB 3441799814 1280 4087
20 Locked QAM256 20 639000000 Hz 10.0 dBmV 42.6 dB 3441814600 1281 4221
21 Locked QAM256 21 645000000 Hz 10.2 dBmV 42.7 dB 3441848349 1296 5121
22 Locked QAM256 22 651000000 Hz 10.4 dBmV 42.6 dB 3441818203 1538 6474
23 Locked QAM256 23 657000000 Hz 10.2 dBmV 42.5 dB 3441858631 1620 6151
24 Locked QAM256 24 663000000 Hz 10.7 dBmV 42.8 dB 3441990008 1566 6080
25 Locked QAM256 26 675000000 Hz 10.9 dBmV 42.1 dB 3442026625 1357 4745
26 Locked QAM256 27 681000000 Hz 10.6 dBmV 42.9 dB 3442174353 1824 4906
27 Locked QAM256 28 687000000 Hz 11.0 dBmV 42.8 dB 3442048948 1477 4859
28 Locked QAM256 29 693000000 Hz 10.9 dBmV 43.0 dB 3442078121 1389 5275
29 Locked QAM256 30 699000000 Hz 10.9 dBmV 43.0 dB 3442181425 1766 6753
30 Locked QAM256 31 705000000 Hz 11.4 dBmV 43.1 dB 3441982299 1548 6314
31 Locked QAM256 32 711000000 Hz 11.2 dBmV 43.0 dB 3442079364 1560 5815
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0
Upstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 35600000 Hz 36.3 dBmV
2 Locked ATDMA 2 29200000 Hz 36.0 dBmV
3 Locked ATDMA 3 22800000 Hz 36.0 dBmV
4 Locked ATDMA 4 16400000 Hz 35.8 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV
Downstream OFDM Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 1, 2, 3 37 762000000 Hz 12.1 dBmV 41.8 dB 1108 ~ 2987 19541840484 9238309562 15881
2 Not Locked 0 0 0 Hz 10.9 dBmV 0.0 dB 0 ~ 4095 0 0 0
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV
Current System Time: Tue Jul 05 14:20:51 2022
System Up Time: 362:59:25