Error when running the "interaction" step: "numpy.AxisError: first argument: axis 2 is out of bounds for array of dimension 2"

[ZianFang]

Hi, I am encounting this error when running snapHiC with a single cell hic contact dataset. I use Python=3.6.1 with the exact dependencies in the requirements. Here is a bug, could you please interpret it for me?
Mon Sep 4 19:32:26 2023: Starting to compute local background
returned size (3952, 3952, 1) (3952, 3952)
yielding (3952, 3952) (3952, 3952, 1)
in compute: (3952, 3952) (3952, 3952, 1)
/data4/fang/opt/SnapHiC/src/interaction_caller.py:211: RuntimeWarning: invalid value encountered in true_divide
local_neighborhood /= local_neighborhood_counts
Traceback (most recent call last):
File "/data4/fang/opt/SnapHiC/snap.py", line 385, in
main()
File "/data4/fang/opt/SnapHiC/snap.py", line 169, in main
n_proc = n_proc, max_mem = args.max_memory, logger = logger)
File "/data4/fang/opt/SnapHiC/src/interaction_caller.py", line 318, in call_interactions
max_distance_bin)
File "/data4/fang/opt/SnapHiC/src/interaction_caller.py", line 220, in compute_significances
ttest_results = stats.ttest_rel(mat, local_neighborhood, axis = 2)
File "/data2/home/zafang/.conda/envs/snapHiC/lib/python3.6/site-packages/scipy/stats/stats.py", line 5759, in ttest_rel
na = _get_len(a, axis, "first argument")
File "/data2/home/zafang/.conda/envs/snapHiC/lib/python3.6/site-packages/scipy/stats/stats.py", line 5675, in _get_len
raise np.AxisError(axis, a.ndim, msg) from None
numpy.AxisError: first argument: axis 2 is out of bounds for array of dimension 2