SM-18 Container decouples anything radially attached to it when its staged
KSP 1.4.3 (MH Only)
KSP 1.11.2 (DLCs only)
When the SM-18 stages detaches its shroud, it decouples anything attached radially
1.4.3 Shows the bug without 1.11 issues and around the time the issue started
Shows issue in 1.11.2 with a bug that seems to happen when physicsless parts are decoupled.
SM18 KSP 143.sfs made in 1.4.3
SM18 Tester.craft made in 1.4.3
Issue happens if the craft is made in 1.11.2, just giving backward compatibility to show when it started.
Thanks go to BezKartuza for showing this issue on the KSP forums and Lisias for additional input to what the cause was.