Seaturtles return to home beach, but don't lay eggs

I have been trying to breed sea turtles. I found two adult turtles, fed them seagrass, and watched them "fall in love". Afterwards, one of the turtles left and went to its home beach. I followed it. However, after it found a sand block, it didn't visibly dig and no eggs appeared. I repeated this process 3 more times with the same results (within the same realm).