I hate

Put bag on floor (rather than fight with the "using your own bag" shit)
Scan a bunch of items, one at a time obviously, and put them in the packing area
Once you've done a bunch then you can lift them all up and put them in your bag which is on the floor.
This should leave the packing area empty ready for your next load of items to scan

What I think happens is that the tills are set to whine/moan if:

• The packing area scales do not increase in weight by the expected amount after scanning an item
  
• The weight goes down a bit, but not all the way back down, e.g. a single item is removed
  
  

but they don't complain if everything has been added one by one correctly and then it relatively quickly goes back to the zero/tare weight.