Yes, the chip is on the back side. The module was designed by our company. What I'm trying to do is a motor runtime counter for a marine engine. They designed this custom board to make the connections easier.
However, I'm currently experiencing the same issue even when I replace the custom board with a standard MCP2515 module. I initially thought it was a connection problem caused by jumper wires, but even if that's the case, it doesn't really explain why the system behaves like it's connected even when the CAN bus isn't active.
For example, I can get this output even when no USB CAN device is plugged in:
09:58:57.763 -> checkReceive() = 3
09:58:57.763 -> ID: 0x404 Data: 0x87 0x87 0x87 0x87 0x80 0x87 0x87
09:58:57.862 -> checkReceive() = 3
09:58:57.862 -> ID: 0x43C Data: 0x87 0x87 0x87 0x87 0x87 0x87 0x87
09:58:57.959 -> checkReceive() = 3
09:58:57.959 -> ID: 0x43C Data: 0x87 0x87 0x87 0x87 0x87 0x87 0x87
09:58:58.058 -> checkReceive() = 3
09:58:58.058 -> ID: 0x43C Data:
09:58:58.157 -> checkReceive() = 4