i updated to 6.220 yesterday and know i experience this;
when i drag a program from the program table to a slot (in the slot rack), that program overwrites the program that was previously loaded in the slot (ie overwrites it not only in the slot rack but also the new program is copied to the program in the program table that previously was loaded in the rack slot).
ive Always done this to change the program of a slot and frankly dont know any other way but now i cant do it without loosing a program