It happened multiple times, that Error has either accidentally opened a portal and walking in on Cross while he was finished with his gym session-- though, at some point, the solider had begun to grow suspicious.

So, he cooked up a plan, and caught Error red-handed, once again "accidentally" walking in on him, all hot and sweaty after a session.

"Wh-what!? I'd never do that on purpose!!" the glitch shrieked, his face flushed as he looked at Cross, who was holding his arms.