Recurring lag spikes and packet loss every 3–5 minutes while gaming despite modem replacement and line repairs

Hi, I’m having a persistent issue with my Xfinity internet connection, specifically while gaming, and I’m hoping someone can help me determine what could be causing it.

I’m experiencing recurring lag spikes/packet loss approximately every 3–5 minutes while playing online games. During the spike, the game will freeze/lag for a moment and then suddenly catch up. The issue happens frequently enough that both games are essentially unplayable.

I primarily play NBA 2K27 and Apex Legends, and the problem occurs in both games. NBA 2K will have severe lag spikes, and Apex Legends does the same. Since it is happening across two completely different games, I don’t believe this is isolated to one particular game’s servers.

What’s also confusing is that I don’t experience noticeable problems while streaming Netflix, YouTube, or other video services. The issue seems to primarily affect real-time online gaming.

Here is everything I’ve tried so far:

• Restarted/reset my modem multiple times.
• Completely unplugged the modem and network equipment, waited, and plugged everything back in.
• Checked my internet connection speeds, which are generally around 400–500 Mbps.
• Replaced my Ethernet cable.
• Confirmed that I am using a wired Ethernet connection rather than Wi-Fi.
• Received a new Xfinity modem, but the lag spikes continued.
• Had an Xfinity technician come to my home and inspect the connection.
• The technician replaced the modem again and also checked the outside wiring.
• The technician indicated that some of the outside wiring/splitters/cabling was old or potentially not functioning properly and made changes/replacements to address that.

Despite all of this, I am still experiencing the exact same recurring lag spikes while gaming.

At this point, I’m trying to figure out whether this could be an issue with packet loss, signal levels, upstream/downstream channels, intermittent line noise, the outside coaxial line, or something else between my modem and the Xfinity network.

Since normal speed tests show 400–500 Mbps, I’m wondering if there is an intermittent connection problem that a normal speed test isn’t detecting.

What would be the best way to diagnose this? Is there a specific test, modem signal information, packet-loss test, or set of logs that I should provide so we can determine where the problem is occurring?

I’d really appreciate any help. I’ve already replaced the modem and Ethernet cable and had a technician inspect and work on the outside connection, but the issue is still happening every few minutes in both NBA 2K27 and Apex Legends.