When i change the material of an element it will no longer be part of the sequencer

hello,
i am trying to change the material of elements that are imported from an ifc file and work with an imported schedule animation, when i try to change the material of certain elements, these elements will no longer be assigned to the sequence animation.
PS the original material has a label that contains : animated material
the elements are under static mesh actors
{4-27 }

thank you in advance !