You are missing the packets where FCtrl = 1 indicates that FOpts contains one byte, and where that byte is 0x0D.
0x0D is “DeviceTimeReq” which is a LoRaWAN v1.1 MAC command not supported by TTN - there are several other threads on that here.
Because MAC commands are variable in length, it is in general impossible for an implementation to safely skip over unknown ones, as it does not know how many bytes to skip. In theory an implementation could simply skip processing anything remaining in FOpts once encountering something undefined and move on to the rest of the packet (since the total length of FOpts is known), however it would appear that the packet is being rejected entirely, and that may well be what the specification formally expects in the case of undefined input.
In practical terms, you will need to work with the device manufacturer to get its firmware to cease sending DeviceTimeReq if you wish to use it on a pre-1.1 network such as TTN. Hopefully this would be part of a more general “make it operate in legacy LoRaWAN mode” as otherwise there may well be other areas where you will trip over incompatibilities between LoRaWAN 1.1 and 1.0x too.