Kowsi KWS-X1 and Voltage Ripple Test

I've been doing ripple testing various power sources using Kowsi KWS-X1. But I found X1 causes sharp spikes at 1MHz interval. Spike length is about one eighth to one thirds of cycles. When I tested 5V mains power transformer based linear power supply, spikes are small and VPP is 7mV. When I tested battery packs, spikes are very big. VPP often reaches over 100mV. AI models say that this is caused by X1's switching regulator of X1 and battery voltage spikes are bigger because of high impedance of battery. This problem make X1's voltage ripple test "useless". I think problem is with the fact X1 does not use own power. So X1 contaminates power. Although knowing this problem is good to me since it can happen to other devices with switching regulator. I may need to get oscilloscope. Any good advice?