I found out from a canadian clarion rep the problem is with a intermittent cable internal in the unit. I will copy the email from him as to what part is needed to repair the intermittent switching problem. You would probably need to take the unit to a repair shop to have the cable installed unless you have some electronic repair experience ie capability of soldering on circuit boards. Below is his the gentlemans email he sent to me along with his contact info of where to obtain the replacement part. I also have the replacement instructions i can provide if you decide to order the part and repair vs replacing the unit. Hope this helps you.
First, let me start by assuming you are in the US. It is not practical for you to send your VX401 to Canada to be repaired, I strongly recommend you use a local repair shop to fix the VX401.
The VX401 switching to Digital Tuner is a problem that we have seen a few times in the past. To correct the problem you need to change a part that has an intermittent failure. This part was used in both the VX400 and VX401. We sold thousands of these 2 models in Canada and have only seen a few with this problem. From our experience, the part you need to change is 3WZ2X01350401 and that should solve the problem. You can order it from PacParts if you are in the US and have your local repair shop install it. It does require disassembling the VX401 but it's not that complicated or difficult, just time consuming.
PacParts: Clarion 3WZ2X01350401
SIRIUS_HD_CABLE - VX400
Administrator, Service Department
Phone: 905.829.4600 X7012
Clarion Canada Inc.
2239 Winston Park Drive
Oakville, ON L6H 5R1