While the scope seems fairly solid and well build I see a lot of signal distortion even when the probes are connected to ground.
Lots of “hair” on leading and trailing edges and peaks.
The first video is connecting to ground with the probe then moved to -5v momentarily, ground, then finally +5v momentarily and back to ground.
Ground Noise with + – 5v transitions.
Internal Signal Generator
With the probe hooked to the internal signal generator. You can see the hair distortion on the peak signal lines.
Sine Wave Distortion
Leading and training edges of the sine wave are badly distorted. Should see clean steps from the signal generator.
Not fuzzy steps with spikes.