When I first started using P5MATE and XIM Matrix, I also had the purple blinking, I replaced the connecting cable between P5MATE and Matrix with another one and the purple blinking stopped.You should all give it a try. It may improve the situation. The cable must be a data communication cable, not a charging cable.
The cable that comes with the Matrix is for data transmission but is not of very good quality. Several people have reported improvements after changing this cable to another one.
Of course, it is tested at 1000 Hz.
The purple flashing did not occur with the C to A cable included with the P5MATE, nor with the commercially available UGREEN 480Mbps data transmission cable.