This thread helped me: https://community.st.com/s/question/0D50X00009Xkb6pSAB/stvd-problems-under-windows-7

I wonder if you ever found an answer. I am also experiencing this problem.I think I can keep it at bay if I only save the workspace before the bug shows up, and never save it after it does. Then close and re open the workspace when I notice it happ...