Kern.err dwc2 Not connected

Model BT Home Hub 5A
Architecture xRX200 rev 1.2
Target Platform lantiq/xrx200
Firmware Version OpenWrt 23.05.2 r23630-842932a63d / LuCI openwrt-23.05 branch git-23.306.39416-c86c256
Kernel Version 5.15.137

Periodically (more than once an hour) I get this message in the system log and my LTE modem is disconnected and has to go through the reconnection process again, which takes 15s to 20s, so it is quite disruptive:

kern.err kernel: [...] dwc2 1e101000.usb: Not connected
kern.info kernel: [...] dwc2 1e101000.usb: NYET/NAK/ACK/other in non-error case, 0x00000002
kern.info kernel: [...] dwc2 1e101000.usb: NYET/NAK/ACK/other in non-error case, 0x00000002
kern.info kernel: [...] dwc2 1e101000.usb: NYET/NAK/ACK/other in non-error case, 0x00000002
kern.info kernel: [...] usb 1-1: USB disconnect, device number 13

Sometimes there are less, or none, of the NYET/NAK/ACK/other info messages.

Any ideas about what might be causing this? Or how I might debug it further?

Thanks!

tried a powered USB hub ?

I don't think it's a power problem because I've already been there and the error messages were different - something like "bad USB cable?" AFAIR. So I enhanced the power supply and those error messages went away...

If this is just a generic error message then I suspect I am getting data transmission errors because the USB2 cable which is 3.5m is just not good enough for this length. It's very difficult to find a long USB2 cable (i.e., >3m) which actually works which is a pain considering the spec for USB2 is supposed to go up to 5m!

use two shorter cables, put the powered USB hub somewhere in the middle ?

Or, equivalently, buy an "active" usb cable, they are not that expensive. My worry about going down that route is that it might introduce additional latency as compared with using plain copper, so, before I try that, I'm going to have go at making one up from some CAT6 ether cable: use 3 pairs in parallel for the power and the remaining pair for the data. I'll report back on the result.
Thanks!