Help for Sevcon Controller troubleshooting Sin Cos warning, sensor issue

[JaJapami]

Hi all,
I have read a few very interesting threads here and thought I should give asking for help with troubleshooting a try.
My electric motor is an Oceanvolt SD-15 motor with a sin/cos sensor. The controller is a Sevcon Gen4 48V 650A, part no. 634A46203, serial no. 1604100312. It is installed on a hybrid sailing catamaran.
A few weeks ago it started to show the “SinCos warning” message and the motor makes grinding noises. We have tried to install a new sin cos sensor, but the problem remains. Also realigning the sensor offset did not work. With a lot of trial and error it will run smooth, but after switching it off and on a few days later, all starts again.
I see that the Uq and Ud voltages of the sensor are always fluctuating when switched off. It should be zero, if I am not wrong.

If you could help me to identify the root cause and a solution I would be very happy and willing to pay for the effort a fair amount.

Thank you and let me know please when you can help.
Cheers
Jan

[Amperry417]

Hello

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[samv76]

you say that after you switch it off and then back on , the problem returns?
Do you have access to DVT software so you can check if the settings in the controller have changed? ( seems unlikely to me)
an oscilloscope to see the encoder signal might be a very usefull tool.

regards,
sander