If I put Samson in the shower, it is a guarantee that he will get rid of some Smegma. Watch him when he poops next and see if you can see him undulating his hemipenis while it is inside him and try to pump some of that old semen out.
One day Samson had some stuck to his vent as well and I just kept it moist and he worked it out on his own. Never fall to the temptation to "help" him out by yanking it out of him as there is a good chance it is still stuck to him