Sim walks to the end of the map.

I play on PS5 and no mods/ expansion packs, only the base game. This is the most bizarre gameplay I have ever experienced. When playing, I noticed that one of my Sims was walking through a lake where you cannot go and can only fish in. His task bar was full and going off the screen that the game had set for him to do; yet he wasn't doing anything other than walking continuously in one direction. The Sim continued to walk off of the map, through houses. Since you can't go past the border in normal gameplay mode, I had to use camera mode to check where the Sim was going. His walk was very slow, it became more like a small shuffle towards the end and after 15 painful minutes, the Sim reached the end of the map and then the game went extremely laggy. I am clueless as why this happened and why this Sim wanted to get to the end of the map. If I tried to pan the camera on him, it would just pan to the end of the location that is loaded that you can't get past even though he was no where near there, he was near the edge of the map.