Null entries in Collections (multi-site)

[ErykSikora]

Hello,
we are preparing to move some our websites to one core which Statamic is.
We have created 2 collections:

• trainings - with 1 site inside (trainings)
• pages - with 2 sites inside (pl, com; both sites with different URLs but with the same layout, default etc.)

so 3 sites in total with different URLs.

Our problem is: Trainings collection shows 0 entries in Collection list ( http://127.0.0.1:8000/cp/collections ).
Moreover: I see blank zone when I'm trying to add a new entry.

I found some clue - I can move "trainings" collection to the top in sites.php, then I can see the total number of entries and I can add new ones....

....but.. then there's a problem with second collection - Pages.

About pages - it's little bit easier, because I can select specified site out of pl and com, but it seems like I don't have selected the default one.

What can I do? Is this any bug?