Actually makes it work by /obj/screen --> /atom/movable/screen

code/modules/client/client_defines.dm

@@ -88,7 +88,7 @@
 
 	var/datum/player_details/player_details //these persist between logins/logouts during the same round.
 
-	var/list/char_render_holders			//Should only be a key-value list of north/south/east/west = obj/screen.
+	var/list/char_render_holders			//Should only be a key-value list of north/south/east/west = atom/movable/screen.
 
 	/// Last time they used fix macros
 	var/last_macro_fix = 0

code/modules/mob/living/carbon/human/species_types/jellypeople.dm

@@ -505,7 +505,7 @@
 		button_icon_state = "slimeeject"
 	..()
 
-/datum/action/innate/integrate_extract/ApplyIcon(obj/screen/movable/action_button/current_button, force)
+/datum/action/innate/integrate_extract/ApplyIcon(atom/movable/screen/movable/action_button/current_button, force)
 	..(current_button, TRUE)
 	if(species && species.current_extract)
 		current_button.add_overlay(mutable_appearance(species.current_extract.icon, species.current_extract.icon_state))
@@ -559,7 +559,7 @@
 			return TRUE
 		return FALSE
 
-/datum/action/innate/use_extract/ApplyIcon(obj/screen/movable/action_button/current_button, force)
+/datum/action/innate/use_extract/ApplyIcon(atom/movable/screen/movable/action_button/current_button, force)
 	..(current_button, TRUE)
 	if(species && species.current_extract)
 		current_button.add_overlay(mutable_appearance(species.current_extract.icon, species.current_extract.icon_state))

code/modules/mob/living/silicon/ai/multicam.dm

@@ -251,7 +251,7 @@ GLOBAL_DATUM(ai_camera_room_landmark, /obj/effect/landmark/ai_multicam_room)
 	to_chat(src, "<span class='notice'>Multiple-camera viewing mode deactivated.</span>")
 
 
-/mob/living/silicon/ai/proc/select_main_multicam_window(obj/screen/movable/pic_in_pic/ai/P)
+/mob/living/silicon/ai/proc/select_main_multicam_window(atom/movable/screen/movable/pic_in_pic/ai/P)
 	if(master_multicam == P)
 		return