"ValueError: Must have equal len keys and value when setting with an iterable" when updating an object type cell using .loc with a nd.array

[isabelladegen]

Pandas version checks

• [X] I have checked that this issue has not already been reported.

• [X] I have confirmed this bug exists on the latest version of pandas.

• [x] I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import numpy as np
import pandas as pd

df = pd.DataFrame({1: [1, 2, 3], 2: [np.zeros(3), np.ones(3), np.zeros(0)]})

print(df.dtypes)

df.loc[1, 2] = np.zeros(3)

Issue Description

The loc assign throws a "ValueError: Must have equal len keys and value when setting with an iterable" despite dtypes being object for column 2. This started to happen when I updated Pandas from 1.4.4 -> 2.2.1. In 1.4.4 this syntax worked. This issue also happens when assigning multiple columns at the same time as soon as one of the new values is an iterable.

Expected Behavior

The assign should set the second row to np.array of zeros.

Installed Versions

INSTALLED VERSIONS

commit : bdc79c146c2e32f2cab629be240f01658cfb6cc2 python : 3.9.19.final.0 python-bits : 64 OS : Darwin OS-release : 23.4.0 Version : Darwin Kernel Version 23.4.0: Wed Feb 21 21:44:06 PST 2024; root:xnu-10063.101.15~2/RELEASE_ARM64_T8103 machine : arm64 processor : arm byteorder : little LC_ALL : None LANG : None LOCALE : en_GB.UTF-8

pandas : 2.2.1 numpy : 1.26.4 pytz : 2024.1 dateutil : 2.9.0 setuptools : 69.2.0 pip : 24.0 Cython : 3.0.9 pytest : 8.1.1 hypothesis : None sphinx : None blosc : None feather : None xlsxwriter : None lxml.etree : 5.1.0 html5lib : None pymysql : None psycopg2 : None jinja2 : 3.1.3 IPython : 8.18.1 pandas_datareader : None adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : 4.12.3 bottleneck : None dataframe-api-compat : None fastparquet : None fsspec : 2024.2.0 gcsfs : None matplotlib : 3.8.1 numba : 0.59.0 numexpr : None odfpy : None openpyxl : None pandas_gbq : None pyarrow : 15.0.2 pyreadstat : None python-calamine : None pyxlsb : None s3fs : None scipy : 1.11.3 sqlalchemy : 2.0.28 tables : None tabulate : 0.9.0 xarray : None xlrd : 2.0.1 zstandard : None tzdata : 2024.1 qtpy : None pyqt5 : None None