Trouble with Havel-Hakimi algorithm

Trouble with Havel-Hakimi algorithm

I am currently developing a custom algorithm for class that implements the Havel-Hakimi algorithm choosing a node randomly. Unfortunately I have run into a logical error that is hard for me to trace (since I am a beginner in programming).I would appreciate it if someone could help me spot the issue. What happens is I get the correct sequence returned sometimes, but other times not

import networkx as nx
import matplotlib.pyplot as plt
import random

def nodes_connected(G,u,v):
    return u in G.neighbors(v)

def hh_graph(seq):
    if not(nx.is_graphical(seq)):
        print("Sequence is not graphical")
    else:
        #Randomly mix the degree sequence
        random.shuffle(seq)
        #Create graph
        G = nx.Graph()
        G.add_nodes_from(range(1,len(seq)+1))
        #Repeat for every node in the sequence
        for i in range(0,len(seq)):
            #j stores number of edges to be added
            j=seq[i]
            #selected node is zeroed
            seq[i]=0
            #Repeat till all edges have been connected
            while j>0:
                k=0
                done=False
                #Repeat till finding a suitable node to connect to
                while k<len(seq) and done==False :
                    #Check to connect to a maximum value node,and avoiding a duplicate connection
                    if seq[k]==max(seq) and nodes_connected(G,i+1,k+1)==False:
                        G.add_edges_from([[i+1,k+1]])
                        seq[k]-=1
                        done=True
                    k+=1
                j-=1
        #Check graph degree sequence to validate results
        degree_sequence = [d for n, d in G.degree()]
        print(f"Graph degree sequence {degree_sequence}")
        #nx.draw_networkx(G)
        #plt.show()

A=[5, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3]
B=[6, 3, 3, 3, 3, 2, 2, 2, 2, 2,1,1]
C=[4,3,2,1]
hh_graph(A)
hh_graph(B)
hh_graph(C)

I have tried to focus on the loops where I think there might be an issue.I have tested different if cases and implementations,but still cant understand how it works half of the time and other times not

Thanks in advance!