I can't answer this without a list so:
Poor management in every store I worked in
Failure to listen to staff as to what times they are available to work - scheduled for wrong days, contradictions between holidays and rota
Taking approved holidays off workers because ''someone asked more recently and we forgot about you''
75% of holidays must be submitted in april for the entire working year, if not holidays are allocated
Pay and tax errors
Failing to address many issues in stores such as faulty heating, broken doors, broken toilets, sinks etc.
Failure to update contracts (moved from 6 hour to 12 hour contract yet still received the lesser holidays for an entire year)
Contracted hours never stuck to - consistently scheduled for at least 5 hours extra each week
Customer Team Members often doing far more work in store than the Team Leaders or Managers despite being paid far less: even having more responsibility than some Team Leaders, ie cash handling, till counting, etc.
CONSTANT understaffing
Far more could be added.