Large holes (defects) in printed objects are almost exclusively caused by dirt on the FEP foil or loose particles in the resin. Tiny pieces of debris on the bottom of the tank will block the light from reaching the resin correctly. Dirt particles also have a tendency to grow during the print, which will increase the size of the hole through the course of the print.
Make sure the FEP foil on the bottom of the tank is perfectly clean. Empty the tank of resin, filtering it with the sieve to make sure any hard particles are not poured back into its bottle. Carefully remove any dirt / solidified bits.
If the FEP foil is cloudy, use hot water and dishwashing soap to clean and restore the original look. The FEP film is rated for 10 prints, but will most often last you longer than that.
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