OKI ES9431 - Faded Print Problem

I have this problem both on Black Only (K) printing and on CMYK color printing.
The colors come out Light, the toner is not dense. (The attached photos are of Black and White printing, but if I print in color the result is the same with the 4 colors, washed out image.

This happened after having Disassembled, cleaned and reassembled the "Black Only" Drum Cleaning Blade (transfer belt).
Assuming that it damaged the Black Drum, I can't understand why the problem occurs on all 4 colors.

Everything was fine before this operation. I only disassembled the blade, cleaned it and reassembled it, I didn't touch anything else nor removed the toner or other rollers. I can't find any solutions, please help me.
@OkiTech

 

[UPDATE 2 - I think the definitive one]

Positioning the Printer temporarily for tests it was close (I would say a few centimeters) to 1 LCD TV, 1 FIRESTICK, 1 POWERLINE (to connect the printer to the lan).

In your opinion, is it possible that these devices created an electromagnetic field that contrasted with the electrostatic charge of the belt so it could not transfer the toner well onto the sheet and a minimal amount of toner came out as shown in the photo, the rest of the image (90/95% remained attached to the belt).
Now I have moved the printer to 1/1.5 mt) it has been printing well for 2 days, I will see what happens in the following days.

Your opinion?