connectivity – Raspberry Pi rock solid on cellular but totally flaky on ethernet

I’m having trouble keeping alive IP connection between eth0 port and laptop on a hard wire. The connection freezes after 5-10 minutes while I am using putty. However, I am having completely zero trouble if I use that same eth0 port (and same wire) to a cellular modem. I can also access the Pi using the bluetooth port to ethernet, and it too gives me 5-10 minutes of connectivity before freezing. In the case of the bluetooth port, I can do it at the same time as the cellular modem through eth0 and in that scenario the bluetooth freezes but the cellular stays alive. Bizarre. (The Pi has WiFi too but that is disabled.)

Any suggestions where I can look at or parameters to watch? I did go through journalctl and didnt see anything. Tomorrow I’m going to try putty via the cellular and try to watch for what happens when the bluetooth freezes.

Thanks,