I tried line2x and line3x. 4x and 5x are out of range of the monitor. Amiga is in the PAL system. It is vertical shaking much more intense than shimmering.
Strange because this monitor displays a very nice image 15kHz in 50Hz with adapter Db23 on vga (dsub) but then we will not get the scanlines.
OSSC ver. 1.6.