I've encountered similar behaviour. It's not a crash, but a very long hang. Some friends have reported hanging for so long they've had to kill the process.
Confirmed for nether portal blocks too (when shift clicking)
That's because you're in creative mode....
When placing a block in creative mode, it is not consumed. That is be design. Change mode into survival and the held item will be removed.
Ahh, my apologies, I did a search for Shulker specific kill commands, didn't think to check against all spawn eggs.
Can't reproduce. Portal frame blocks are directional, the easiest way to make a functioning portal is to stand in the centre of the 3x3 area, then place portal frames around you. Now all the frame blocks will be in the correct orientation, and your portal will be activated.
Can't reproduce with any GUI block, with or without torches in the off-hand slot.
Please try again, checking that you do collect a lava bucket before opening the hopper GUI, and that you didn't miss when collecting lava.
Still present in 15w31c
Also occurs in 15w31b.
Not shown in these screenshots is that the shulker appears to teleport rapidly between it's original location, that of the moving entity, and a point half way between these two. All three versions of the shulker have a bounding box, but only the shulker on the moving entity blocks movement or takes damage.
Also, bounding box of shulker obscures that of minecarts, making breaking of minecarts impossible. Larger entities such as cows & horses can still be hit whilst being ridden by shulker.
Can confirm for carrots, potatoes and cocoa in 1.12 release.