Created attachment 144227 [details] these are the exact conditions at which the event occurs SUMMARY *** NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols. See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports *** I tried this in different conditions and sequences, but the freeze should generally work if the particle is anchored (and maybe attached to a spring) STEPS TO REPRODUCE 1. Launch step. 2. Take a particle. 3. Anchor it. 4. Set its mass to 0. 5. Try to launch the simulation. OBSERVED RESULT Step stops responding EXPECTED RESULT I am not sure what I was expecting, but I think I wanted to eliminate any gravitational influence on the spring while having it anchored (the dumbest idea, but ok) SOFTWARE/OS VERSIONS Windows: no macOS: still no Linux/KDE Plasma: Arch Linux with KDE plasma. (available in About System) KDE Plasma Version: 5.23.4 KDE Frameworks Version: 5.88.0 Qt Version: 5.12.2 ADDITIONAL INFORMATION the