When GLOBAL TEMPORARY TABLE's is re-created and sweep run at the same time wrong page type error may occurs.
To reproduce run following statement

execute block returns (sql varchar(255))
as
declare n int;
declare i int;
declare s varchar(256);
begin
  n = 0;
  while (n < 20) do
  begin
    i = 1;
    while (i < 10) do
    begin
      s = 'tmp' || :i;
      sql = 'create global temporary table ' || :s || ' (id int);';
      execute statement sql with autonomous transaction;
      suspend;

      sql = 'drop table ' || :s || ';';
      execute statement sql with autonomous transaction;
      suspend;

      i = i + 1;
    end
    n = n + 1;
  end
end

and run gfix -sweep while statement above is executed.