(simlab) *** ERROR: error occurred executing acuSolve" How to fix it ?

Hi guys. I followed this tutorial "Piezoelectric Flow energy Harvester : A fluid structure interaction (DC-FSI)

I already set up mesh and solution but when I started update solution in Coupled Solution (Flow - Structural) I faced this problem 

in Solving log files 

---------------------- Begin Time Step ----------------------

acuSolve: Time-Step= 1 ; timeInc= 1.000000e-002 ; time= 0.000000e+000

acuSolve: External-Code stagger "external_code":

acuSolve: For all structural external_code_surfaces:

acuSolve: Ave fld-sld mesh gap = 2.245669e-009

acuSolve: Max fld-sld mesh gap = 7.731059e-007

acuSolve: Min allowed gap = 9.654899e-009

acuSolve: Max allowed gap = 1.712737e-008

acuSolve: *** ASSERTION in Function <ecdSetFatalError> File <ecd.c> Line <4324>

acuSolve: *** Fluid mesh unable to track external surfaces at 27 quadrature points,

the gap between them exceeds allowed value.

If a tight limit is set for allowed gap, try increasing it.

If the limit is loose, then external surfaces have large movements,

which could be expected, try reducing time step size

acuRun: *** ERROR: error occurred executing acuSolve"

acuRun: Thu Jul 22 10:11:34 2021


Does anyone faced this similar problem or anyone can suggest me to fix this problem ?  Thanks