(Not yet tested in Explore.)
Found what seems like 2 kinds of bugs with the new blocks, but they might be slightly different versions of the same problem.
The 1x2x2 Marble Block circled in blue will place but will not allow me to select it again by clicking. I have to click/drag a large area around it to get it to select.
The 3 blocks marked with red do what's pictured in the screenshot. The lower left reference point is where I placed the blocks. The collision box is there, I can select them by clicking the "empty" space, and it will show the object name if I put my mouse over it. The visible model, however, is at the upper right reference point. The two points are 57.375 apart on the X, and 31.125 apart on the Y.
I am still checking, so there could be similar bugs with other kinds of blocks. Just wanted to get this added to the list. I'll add to the thread if I find more.