[woronczak]

Any thoughts? 

Its not your box or connection. Most likely the source your media is playing from is bad or congested. Another reason might be that your ISP is throttling your speeds download a vpn from the playstore and try again. 

Hi,

Thanks but I don't get it. These files are streamed locally, as everything is stored in a NAS. The ISP cannot be involved...

Also, if I stream from my laptop everything works fine and Kodi never has the need to buffer, so I don't think it's the NAS to be honest. My suspicion is that the 5ghz bad on the mibox is the culprit... 

 Wifi on the MiBox is average. Much more solid connection with USB Lan adapter as discussed earlier in this thread. We have a good router maybe 3m from a MiBox (admittedly there is part of a wall in the way) and the signal is not very good / stable (for streaming bluray rips from a local server), whereas from a laptop / Wetek Play 2, it is fine. The only way I could get reliable & fast wifi connection was to have a router literally next to the MiBox (hence much better to use the USB Lan adapter). Wifi might be OK for Youtube / Netflix but for higher bitrate files, you can't beat cable.