Use different variables for lettings and sales postcode known

app/models/log.rb

@@ -248,7 +248,11 @@ class Log < ApplicationRecord
   end
 
   def blank_compound_invalid_non_setup_fields!
-    self.postcode_known = nil if errors.attribute_names.include? :postcode_full
+    if errors.attribute_names.include? :postcode_full
+      self.postcode_known = nil if lettings?
+      self.pcodenk = nil if sales?
+    end
+
     self.ppcodenk = nil if errors.attribute_names.include? :ppostcode_full
     self.previous_la_known = nil if errors.attribute_names.include? :prevloc
 
@@ -259,7 +263,8 @@ class Log < ApplicationRecord
       self.address_line2 = nil
       self.town_or_city = nil
       self.postcode_full = nil
-      self.postcode_known = nil
+      self.postcode_known = nil if lettings?
+      self.pcodenk = nil if sales?
       self.county = nil
       process_postcode_changes!
     end