Decouplers not working, empty rockets not being dropped.

I'm having an issue hopefully someone can help me with. I haven't played since .16 but downloaded the new update, and often I find that a group of rockets will stay attached to my main rocket even after the decouplers fire.

Here's a super simple setup I just did. Double sized fuel tank with rocket at the end, 3 decouplers around the outside to 3 solid rocket boosters. The staging is correct. When I fire the rocket everything looks normal, then when the rockets finish I press space and theres an animated explosion(no fire) to show the decouplers unlinking, and then bam! The three solid stage rockets are now listed in the same stage as the middle rocket even though they're all empty, and the decoupler stage is gone!

Please help me fix this, it's preventing me from doing any of the larger sized rockets.