Did you thin the data or erase it entirely? If you merely thinned it, your sequence may still contain data you don't need at all (controller data your patches don't respond to anyway) and that takes up memory.

Did you ever go into microscope mode to see exactly what it was you were deleting? I'm curious to know what it was.

For all you know, you may have been deleting the winning lottery numbers for tomorrow night . . .