BD grey screen and no menu on mac mini

Dear experts,

I've just started to play my BD with VLC on mac mini, since it's zone free. I'm using an I/O external USB player and the mini is a mid 2011, osx 10.12.1, 8gb 1333 ram, and it's used only as media player, so no data inside

Everything is running smoothly (DTS & Dolby recognized by the AVR, video ok) and better on any aspect than the PS3 I was using, but I have 2 main problems

- where I can find the start menu like in the normal BD player?
- especially in the "fast" scene, I got a "grey screen", and VLC skips 2/3 second of movie before "loading" it again, like it was buffering something

do you think the mini can replace a full BD player?
am I using the best player for the scope?
do you have any recommendation on how to fix my problems of "buffering"?

thanks in advance for the help!!

cheers