Fixes the other thing

code/game/objects/items/devices/modificationkit.dm

@@ -18,6 +18,12 @@
 		user << "<span class='warning'>This kit can only modify kinetic \
 			accelerators!</span>"
 		return ..()
+	// RIP the 'improved improved improved improved kinetic accelerator
+	if(C.holds_charge && C.unique_frequency)
+		user << "<span class='warning'>This kinetic accelerator already has \
+			these upgrades.</span>"
+		return ..()
+
 	user <<"<span class='notice'>You modify the [C], adjusting the trigger \
 		guard and internal capacitor.</span>"
 	C.name = "improved [C.name]"