Hi,
Thanks for writing in. Recurrent inflammation of testicles can be due to obstructed epididymal, STD’s etc. But hard testicles could be due to atrophy or tumors. The common complications of mumps orchitis are testicular atrophy, shrinkage of testicles.
I would suggest that you repeat a scrotal ultrasound , semen analysis and visit a urologist for further assistance.
Best.