Wrong output generated while loading bags as input

A = LOAD '/user/pvivek/sample' as (id:chararray,mybag:bag{tuple(bttype:chararray,cat:long)});
B = foreach A generate id,FLATTEN(mybag) AS (bttype, cat);
C = order B by id;
dump C;

The above code generates wrong results when executed with Pig 0.10 and Pig 0.9
The below is the sample input;

...LKGaHqg--	{(aa,806743)}
..0MI1Y37w--	{(aa,498970)}
..0bnlpJrw--	{(aa,806740)}
..0p0IIhbA--	{(aa,498971),(se,498995)}
..1VkGqvXA--	{(aa,805219)}

I think the Pig optimizers are causing this issue.From the logs I can see that the $1 is pruned for the relation A.

[main] INFO org.apache.pig.newplan.logical.rules.ColumnPruneVisitor - Columns pruned for A: $1

One workaround for this is to disable -t ColumnMapKeyPrune.