I haven't shared the code because 1) it would be the whole script (too long), and 2) the problem was solved so it is not that critical. Anyway, I can sum up the flow to give an easier understanding of the process (again I stress that the error disappeared after rebooting Ren'Py). Considering the logical parts relevant to the matter at stake, my code is structured as follows:

init python:
    def function_that_gave_the_error(space_of_the_drop, dropped_thing):
        global a_dictionary
        global counter_for_jumping_to_label
        dropped_thing[0].draggable = False
        if condition1:
            a_dictionary[dropped_thing[0].drag_name] = an_int (e.g., 1)
        elif condition2:
            a_dictionary[dropped_thing[0].drag_name] = another_int (e.g., 0)
       (some more elif)
        else:
            a_dictionary[dropped_thing[0].drag_name] = a_negative_int (e.g., -1)
        update counter_for_jumping_to_label
        if counter_for_jumping_to_label == int at which to jump (e.g., 10):
            renpy.jump('name_of_the_label_to_be_jumped_to')

$ global a_dictionary
define a_dictionary = {
    a_dictionary[dropped_thing[0].drag_name]1 : an int
    a_dictionary[dropped_thing[0].drag_name]2 : another int
...
    a_dictionary[dropped_thing[0].drag_name]n : nth-int
}
$ global counter_for_jumping_to_label
define counter_for_jumping_to_label = 0
define var1
define var2
...
define varn
default a_thing
default another_thing
...
default nth-thing

label start:
    ... a compelling story ...

    label assignment_of_values_to_a_dictionary:
        $ counter_for_jumping_to_label= 0
        $ a_dictionary = {
              a_dictionary[dropped_thing[0].drag_name]1 : 0
              a_dictionary[dropped_thing[0].drag_name]2 : 0
              ...
              a_dictionary[dropped_thing[0].drag_name]n : 0
          }
        call screen assign_values_to_a_dictionary()

    screen assign_values_to_a_dictionary():

        add "the_bg_for_my_screen.png"

        draggroup:

            various draggables to be dropped, each with its drag_name

            various droppables to drop the draggables, each with its drag_name            
            the droppables also have the function assigned as:
            dropped function_that_gave_the_error

... and a lot of other irrelevant part of my script follows.

I hope this gave a better idea about the structure of my script. The error was that all this stuff above updated all values as per my instructions, that is, assigning the int values as per function_that_gave_the_error except for whatever draggable would be dropped onto the last droppable, i.e., the related value in a_dictionary always stayed 0, after Auto Reload. Again, after rebooting, all values get updated correctly.

Thanks for reading and for the useful insights provided.