Singularities in the shape

Hi all

I am modelling a single cell passing through a microfludic device in 2D set up using fluid-solid interaction interface(FSI).

I found that when the velocity of the fluid is extremely high in the channel, in my model there are some singularities, however the deformed shape from the experiment should be a rather smooth "bullet" shape.

I used the creeping flow to simulate shear flow. For the material model, I used neo-hookean incompressible material model. Besides, I also added three boundary loads except default interfacial force.

I attached the figures from the experiment and simulationIs. Is there any way to smooth the fluid-solid interface or get rid of the singularities?