Some topics have topic words starts with same letters or end with same letters

Hi @MaartenGr, I want to thank you for developing bertopic, as it has been instrumental in the smooth progress of our project. And I am truly grateful for providing us such an active/progressive discussion and solutions.

I am dealing with 2 million documents and below is the main code:

`
from bertopic import BERTopic
from hdbscan import HDBSCAN
from umap import UMAP

import numpy as np

from sentence_transformers import SentenceTransformer
sentence_model = SentenceTransformer("all-MiniLM-L6-v2")
embeddings = sentence_model.encode(docs, show_progress_bar=False)

from sklearn.feature_extraction.text import CountVectorizer

umap_model = UMAP(n_neighbors=15, n_components=5,
min_dist=0.0, metric='cosine', random_state=42, low_memory=True)

vectorizer_model = CountVectorizer(ngram_range=(1, 2), stop_words="english", min_df=100)
model = BERTopic(vectorizer_model=vectorizer_model, umap_model=umap_model, calculate_probabilities=False, nr_topics=500)

topics, probabilities = model.fit_transform(docs)
red_topics = model.reduce_outliers(docs, topics, strategy='c-tf-idf')
model.update_topics(docs, topics=red_topics, vectorizer_model=vectorizer_model)
`
And I found some of the topics are just the group of topic words starting with same letters as
(I made them up to just give some examples)
'xabvd, xser, xwesd, xrfde'
'jfrsd, jresa, jliok, joiun'
'dau' 'dan' 'daud'
or ends with same letters as
'calcium' 'valium' 'xxxxium'

Does this come from CountVectorizer? And is there any way to fix this?
Thank you so much!

Respectfully,
Ji Hyun

Start with the provided BERTopic example and inspect the CountVectorizer configuration, then trace how fit_transform and update_topics produce the displayed topic words. Compare the resulting vocabulary and topic representations with the reported prefixes and suffixes. Done means establishing whether the behavior originates in CountVectorizer or another named component and documenting a reproducible fix or configuration.