That's how Kodi is by design and always has been, its not a fault or bug, the buffer is there for the opposite reason than what you are expecting it to be there for.
If your internet is slow then I don't think streaming is for you, you can increase the buffer and pause a video until the buffer is full and this will help on smaller videos but it won't help much on larger videos. Try limiting your sources to non-HD as well.
I will keep an eye on that. Actually I do have 10/10Mbit/s internet, so it should not be me for less than 4k.
This may be out of context but it quite nicely describes my problem, whereas for me it is occurring also for other video addons. Also the frame sometimes stops, stutters with or without sound or freezes completely.
Frame and sound stuck after buffering · Issue #247 · asciidisco/plugin.video.netflix · GitHub
Let's stop here, I will run some tests and come back with a log file in case it persists.
I'm looking forward for the new build! Happy New Year!
Update: It just happened again, the video freezes showing the buffering ring at 5%. I waited 2 minutes, no change. Jumped 10s further, video continuous to play within 1s. If anything would be too slow, why the video plays within 1s after moving further in time.