Kodi stops buffering ahead, no matter how long I wait

I’m using Kodi 16 RC 3 on an Android 5 device (Matricom G-Box 2) and all videos play flawlessly when reading from local storage (or SD card). But when I stream wirelessly from remote sources (either local NFS or Internet sources), it stops reading ahead (only fills a tiny portion in grey) no matter how long I pause the video and wait (even a couple hours), and no matter the size or resolution of the video.

Isn’t it supposed to buffer a sizable chunk ahead of the current moment, even longer if I wait longer? Is there any way to modify this? (I’ve already tried Advanced Settings XML and it doesn’t seem to change this behaviour)

Greetings and thanks in advance,

(NOTE: I’ve already tested the connection speed, it doesn’t seem to be the problem, I get 7-10 Mbps)
(NOTE2: No, I DON’T use illegal add-ons, I’m only using legal sources and local files on plain Kodi, even deleted my whole configuration and started over)