Missing USB ports is problem of device tree blob. For fixing KI Plus replace dbt.img with gxbb_p200_k1_plus.dtb (rename it to dbt.img).
For KII Pro I fixed dtb in #1. Bluetooth adapter will be fixed in next release.
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In my K1 PLUS Wifi only works for a few minutes after starting. On another router is the same. Does anyone have a solution to this problem?
This is know issue. WiFi has only week internal patch antenna. WiFi is useable only for short distance. You can improve your box installing external antenna (e.g. using antenna from old wifi router).