Thank you for your response!
I have tested the system with the adhesion model turned off and the system behaves normally. The number of particles in the system remains constant. However, as soon as the JKR adhesion model is turned on with a surface energy setting of 0.01 J/m2, some particles are deleted at the same impact and timestep, and other settings. I have attempted to reproduce the same model that I was using in Rocky DEM in EDEM, and I have found that the model works fine with a timestep of 1e-6. However in ROCKY i decreased the timestep to 1e-8, although there are fewer missing particles, some are still disappearing.
Is there any known solution or workaround for this issue with the JKR adhesion model causing particle deletion? Any suggestions would be greatly appreciated.