Error: unknown event type 37?

I have a Sierra Wireless MC7430 USB 3.0 LTE modem running on a custom board which is based on the MT7621A SoC. I'm using the USB 3.0 drivers. Lately it seems when I do anything bandwidth-intensive such as a speed test, or after at least 9 hours of uptime with normal usage, I will start seeing this "event type 37 error". I can't be sure yet but it seems like it usually happens after the bandwidth has gone above 40Mbps. Occasionally the modem cannot recover (unsure if this is the cause, but seems likely at this stage) and needs to be reset, which means rebooting the board.

Any hints on what this is, or the cause? I read that this might be the usb controller's ring buffer becoming full, but can't confirm.

[  242.657691] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
[  244.717622] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37

USB Kernel modules, and I am on kernel 4.14.95, OpenWrt 18.06.2.

kmod-usb-acm - 4.14.95-1
kmod-usb-core - 4.14.95-1
kmod-usb-net - 4.14.95-1
kmod-usb-net-cdc-ether - 4.14.95-1
kmod-usb-net-cdc-mbim - 4.14.95-1
kmod-usb-net-cdc-ncm - 4.14.95-1
kmod-usb-net-hso - 4.14.95-1
kmod-usb-net-huawei-cdc-ncm - 4.14.95-1
kmod-usb-net-qmi-wwan - 4.14.95-1
kmod-usb-net-rndis - 4.14.95-1
kmod-usb-net-sierrawireless - 4.14.95-1
kmod-usb-serial - 4.14.95-1
kmod-usb-serial-option - 4.14.95-1
kmod-usb-serial-qualcomm - 4.14.95-1
kmod-usb-serial-sierrawireless - 4.14.95-1
kmod-usb-serial-wwan - 4.14.95-1
kmod-usb-wdm - 4.14.95-1
kmod-usb3 - 4.14.95-1
libusb-1.0 - 1.0.22-1

https://lists.gnu.org/archive/html/qemu-discuss/2017-12/msg00006.html seems related and mentions

Qemu gives me this error message before it sends that event type 37 (CC_EVENT_RING_FULL_ERROR):

Sounds like what I'm seeing!

I am seeing the same problem on a Unielec U4019 with a Sierra Wireless EM7565 after running a speed test

Linux OpenWrt 4.19.78 #0 SMP Tue Oct 22 22:52:45 2019 armv7l GNU/Linux

Tue Oct 22 23:01:22 2019 user.notice firewall: Reloading firewall due to ifup of mobiledata (wwan0)                                                           
Thu Oct 24 00:21:15 2019 user.info banIP-0.3.1[7935]: banIP is currently disabled, please set ban_enabled to '1' to use this service                          
Thu Oct 24 00:21:25 2019 user.notice vpnbypass [8338]: service monitoring interfaces: mobiledata ✓                                                            
Thu Oct 24 00:21:26 2019 user.info banIP-0.3.1[8572]: banIP is currently disabled, please set ban_enabled to '1' to use this service                          
[  374.953747] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
Thu Oct 24 00:23:56 2019 kern.warn kernel: [  374.953747] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
[  380.026621] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
Thu Oct 24 00:24:02 2019 kern.warn kernel: [  380.026621] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
[  381.399986] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
Thu Oct 24 00:24:03 2019 kern.warn kernel: [  381.399986] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
[  386.087302] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
[  386.119498] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
[  386.151367] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
[  386.183377] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                                                                          
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.087302] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.119498] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.151367] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.183377] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.244467] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.276268] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37                                               
Thu Oct 24 00:24:08 2019 kern.warn kernel: [  386.308029] xhci-hcd xhci-hcd.0.auto: ERROR unknown event type 37

I'm getting it too. I recon doing a speed test during the log appeared. Using Xiaomi R3G with a m.2 to USB adapter for Quectel EM12-G

Tue Sep 22 07:31:20 2020 kern.warn kernel: [254217.726089] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:20 2020 kern.warn kernel: [254217.733656] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:20 2020 kern.warn kernel: [254217.741929] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:20 2020 kern.warn kernel: [254217.750078] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:20 2020 kern.warn kernel: [254217.758078] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:22 2020 kern.warn kernel: [254219.499136] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:25 2020 kern.warn kernel: [254222.360244] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:25 2020 kern.warn kernel: [254222.367636] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:25 2020 kern.warn kernel: [254222.374973] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37
Tue Sep 22 07:31:25 2020 kern.warn kernel: [254222.705130] xhci-mtk 1e1c0000.xhci: ERROR unknown event type 37

Guys, getting this as well (ZBT WG1608 router).
This is annoying because it is likely reducing the throughput of the modem.
What is the point of a 5G capable router if the kernel can't handle the faster speed
due to a driver's insufficient ring buffer?