But there are some 1Vpp spikes on the output. They are about 100ns wide. Is this OK and normal??
The Mean Well GS60A12-P1J PSU was loaded with a 4 ohm power resistor. The measured frequency is often false because the waveform is quite complex.
Please note that the scope was set to AC coupling.
EDIT: Note that the automatic frequency measurement is often not correct on such a complex waveform.