I don't have this problem, but I know someone who did.
She simply cut down on the quantity of Epsom Salts (by half), her problem settled down on the second flush and out came the green balls and the runny's finished that first day. Evidently her system was more sensitive to the salts than most people. Maybe your is also.
FYI, I seemed to be able to handle a little more so I increased the Epsom Salts by about 25%. I am typically still having running stools until early on flush evening (AND GREEN BALLS COMING ALSO), but have it "under control" by early afternoon, ie, I won't leave the house until 1 or 2 pm on the flush day. But on the second and third days the stools are a little loose, but not bad. With the recommended dose of salts I was out by noon with firm stool that evening, but it was not as successful (I think).
Don't give up.... just tweek the salts to match your system.