The paper feed adjustment wheel

At the centre of the paper feed tray, just below the feed tray descent button, is a rubber wheel which is responsible for moving the sheets from the tray inside the machine. Because the ink is not completely fixed and is still wet, the colour that is already on the print sheet may give off ink to the underlying sheets due to the overlay of the paper under the rubber wheel or when the rubber wheel is moved across the sheet being printed. There are several ways to avoid this:

The rubber wheel can be cleaned with cleaning agents such as WD-40 or alcohol containing solutions. This may take a while and should be repeated a few times to make sure that all the colour pigments are removed from the rubber wheel. Papers that are printed immediately after cleaning seem to exhibit more colour abrasion because the colour dissolves from the rubber wheel due to the cleaning substance.
Select a paper size that provides enough space around the feed wheel or brighten up the subject so there is less ink under the rubber wheel.
Start printing on the side of the sheet with less ink coverage.
Turn the document over by using the 180 ° turn option in the RISO driver so the weakly coloured side is under the rubber wheel.

If these points are impossible to comply with for production reasons, the following tips may help prevent colour abrasion:

Increase the drying time of the sheets. The colour may appear drier because of more discarded water particles
Carefully spray the sheets with fixative spray or hairspray at a distance of about 30—40 cm to make the colour a little more resistant. Caution: Depending on the spray (especially with hairspray), the sheets may shine a little. Additionally, there must be enough space between the hairspray and the substrate to avoid too much spray being applied on a small paper surface, thus dampening the paper and changing the structure of the colour