Automatic transmission

Hi, can anyone help me with this? I have a 2001 Ford Escape 4x4, and three months ago I took it on a sandy beach. It worked perfectly, as if it were on solid ground. A week ago, I took it back to the same spot, and now it won't move or it's going very slowly. I decided not to risk it getting stuck. It seems to be shifting gears fine, or maybe the four-wheel drive is worn out. I'm new to this, so can someone please tell me what to do?

Perhaps the transmission discs are worn out and slipping, and you need to repair the transmission. Regards

Hi, getting back to the topic, if it were the discs, they would also slip when driving off-road, like on the road, but not at all. The gear changes are smooth and effortless, that's why I'm worried it might be something else. It's normally front-wheel drive. Can anyone give me another suggestion?