Volume changes abruptly when seeking in a video

Reproducibility: 100% , with more or less seeks. Meizu Pro 5 OTA14

1-play a video (in my case, a camera-recorded video)
2-tap on any position in the bottom bar to seek to this position in the video
3-repeat step 2 until the volume instantly becomes as loud as the "speakers volume" you configured for your phone to ring.

Usually, 2-3 seeks reveal this annoying bug.

By the way, I would also like a feature to set the in-app/in-video volume BEFORE starting an app/hitting play. Do you know where can I report this missing feature?