Help with SQL Update using join files

I have the following SQL statement:
update vinbini set baqcm = (select ifqcm from vinitmb join vinbini
on bacmp = ifcomp and baloc = ifloc and baitem = ifitem
where ifqcm <> baqcm and babloc = 'WHS')
where exists (select 1 from vinitmb join vinbini
on bacmp = ifcomp and baloc = ifloc and baitem = ifitem
where ifqcm <> baqcm
and babloc = 'WHS' )

Where file vinitmb is unique at the company/location/item level and vinbini
is unique at the company/location/item/bin level.
I want to update a field in vinbini for the 'WHS' bin records only when the
committed qty in vinitmb does not equal the value in vinbini.
I am receiving the Result of SELECT more than one row message.
What am I missing?

Thanks,