Female led relationships discussion

To start again, I’m new here but loving it! My slave has been locked up for a month or more now and handling it really well. He looks after me and follows my instructions closely. He’s turned into a very caring partner who satisfies me greatly. The other night while we were having fun, he groaned and said, “I’m cumming!” and I didn’t realize what was happening until the moment passed. Does this occur occasionally for caged slaves? I suspect his cage might be slightly too large and needs swapping out; also, perhaps I teased him more than I should have. There wasn’t any thrusting involved, but suddenly he hit that point of no return. He clearly didn’t want it to happen and was let down when it did. Has anyone else experienced this? What causes it?