Parking Radar issue

Hello,
I'm having some trouble with my parking radar. When I shift to R the tweeter is playing a continuous beep in a bad tone like it's defective. After 5 seconds it stops and the sensors does not detect anything near them. I had the issue before but if I switched to D and back to R the radar worked fine.
I checked the radar module in the rear but I'm not sure if it's the root cause. It gets voltage, also the tweeter works even if it's in a bad tone. It's an OEM Toyota PZ464-B4420-01. I did not find anything related to this and I don't want order a new one from the junkyard until I'm certain.
Thanks in advance.