Flex particles whose mass are infinity will not stay in position when there are fluid particles at the same time

Hi everyone,

I just noticed there is a difference as I stated in the title. When there are only solid particles (rigidbody or softbody) in my simulation, if I set the mass of some of the particles on an object to infinite, those particles will stay in place when I drag the object because those particles have infinite mass and cannot be moved as we all know. But if I have fluid particles in the simulation at the same time, I noticed those infinite mass particles on those softbody can be moved along when I drag the object. Even though the softbody is still bouncing back to the same still location when you release the object. However, there is no difference to the visual effect of the simulation of the mesh. I’m just saying, when you turn “draw particles” on, you can see the difference. Can anyone explain this to me?