Anybody have any experience with "Service Recommended for SPC" message on a 550c. I found a bulletin about replacing the sensor and installing a mylar. I disabled the drum potential sensor with 08-2561 but the message keeps returning.

I googled and found this info. Only other info is to turn off sensor.

Check the control status of the surface potential sensor (05-242).
<When “4” is displayed: sensor error>
The sensor detection value is abnormal or the sensor output value is not changed even though
the main charger bias value is changed.

Is the connector of the surface potential sensor connected properly?

Is the main charger grid/wire attached poorly?
Is the main charger attached poorly?
Are leaks and such occurring?