You may have an Alternate Text entry for some other tag. With the PDF open, display the Tags panel. Use the Options menu and select Properties. Display Properties dialog's Tag tab. Position the Properties dialog off of the Tags panel. Now, top down, walk the structure tree. As you select each tag its properties are displayed in the Properties dialog. Some where in the tree there is a tag having a Alternate Text entry. Once located, deleted and tab to another field in the dialog to assure the edit "sticks".
You may have an Alternate Text entry for some other tag.
With the PDF open, display the Tags panel.
Use the Options menu and select Properties.
Display Properties dialog's Tag tab.
Position the Properties dialog off of the Tags panel.
Now, top down, walk the structure tree. As you select each tag its properties are displayed in the Properties dialog. Some where in the tree there is a tag having a Alternate Text entry. Once located, deleted and tab to another field in the dialog to assure the edit "sticks".
Be well...