blender symmetries are weird. It works strangely When I made the chest, I mirror the ball on my body and used join.
The symmetries, which worked well in the face, became not the x-axis of object standards as shown in the picture.
What should I do?
If I am not mistaken, your object origin has moved. Try resetting it.

Enable &quot;Affect Only Origins option&quot; (see image)
Select your object in object mode and hit Alt+G to reset its transfrom


Or

Shift + C to reset cursor.
right click -&gt; set origin -&gt; to cursor