WARNING - A MAP or COMMON with the same name exists in more  than  one
  program  module,  and first one encountered by the compiler is smaller
  than the subsequent ones.  BASIC first allocates MAP and COMMON  areas
  in  the main program, then MAP and COMMON areas in subprograms, in the
  order in which they were loaded.  Thus, you can avoid  this  error  by
  loading  modules with the largest MAP or COMMON first.  However, it is
  better practice to make MAP and COMMON areas equal in size.