This issue doesnot occur every time.

When I try to adjust the size of the text box in a slide by dragging the frame, it just return back to the previous position. Any ideas are appreciated.

Hello,

You can modified the size property of the "frame". Steps:

Select the frame (Make sure you have selected the border and see the cross icon) =>Right click =>Size and position =>Modify the value of the size property.

Regards,