BankStack is the leading cause of things moving in your bags and bank.

It:

sorts your inventory, bank, or guild bank

fills incomplete stacks in your bank with items from your inventory

compresses your bags by filling incomplete stacks within them

puts a chicken in every pot, and pot in every chicken

Quick command reference:

/bankstack : show configuration

/sort : rearrange your bags

/sort bank : rearrange your bank

/stack : fills stacks in your bank from your bags

/stack bank bags : fills stacks in your bags from your bank

/stack {group1} {group2} : fills stacks in group2 from group1

/compress : merges stacks in your bags

/compress bank : merges stacks in your bank

/compress {group} : merges stacks in group

/fill : fill empty slots in your bank from your bags

/fill {group1} {group2} : fill empty slots in group2 from group1