This looks like the modem tries to initiate low power USB states, but that fails for some reason. which probably leads to more trouble when the host tries to “fix” the issue. Interestingly enough, a patch fixing precisely such a problem in dwc3 was posted to linux-usb today: spinics.net/lists/linux-usb/msg161124.html
Note that the MC7455 USB device controller is a dwc3 IP from Synopsis integrated in the MSM chipset. Hard to say if this is relevant, as the driver probably is a heavily patched version for the Qualcomm MSM chip. And that driver could have this fix already for all we know.