Such problem can happen when there is long thin layer, curved surface touches a plane, or sharp corners. In your case, if it is not from thin layer,it is likely from the sharp tips of the pyramid. If so you may need to smooth it, or try to reduce the triangle sensitivity, or deflection:
 
You may refer to this post  : https://optics.ansys.com/hc/en-us/articles/8355464963987-Troubleshooting-convergence-errors-in-CHARGEÂ
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