Running Windows 10 Pro and Illustrator v 25.1.
Opened existing illustrator file
Unlocked a layer of my design
Attempted to select all items within that layer.
Expected: Items are selected and can be manipulated
Actual: Illustrator stopped responding.

I attempted to select the items multiple ways, including the "Click to target..." circle to the right of the layer in the Layers window, using Ctrl+A, and using the Selection Tool.

I cannot provide my file, but I will provide further details:

The top layer that I had unlocked included many groupings nested within it. I was able to reproduce the issue with some sub-layers, but not others.

One sub-layer is a Braille alphabet representation that includes 26 groupings of 6 ellipse objects, each of which appears separately in the Layers window. Notably, a similar layer of 26 groupings of 1 ellipse and 2 lines each (graphical representation of flag semaphore alphabet) can be selected with no problem, despite a similar Layer structure. The Braille has 156 base objects, and the Flag semaphore has 78.

Problem signature
Problem Event Name: AppHangB1
Application Name: Illustrator.exe
Application Version: 25.1.0.90
Application Timestamp: 5fe2488c
Hang Signature: 22d0
Hang Type: 134217728
OS Version: 10.0.19041.2.0.0.256.48
Locale ID: 1033
Additional Hang Signature 1: 22d047c84bbb39d272b6071d7179c59b
Additional Hang Signature 2: 629c
Additional Hang Signature 3: 629cc9817ef4a2fae3b3acc720fdec68
Additional Hang Signature 4: 22d0
Additional Hang Signature 5: 22d047c84bbb39d272b6071d7179c59b
Additional Hang Signature 6: 629c
Additional Hang Signature 7: 629cc9817ef4a2fae3b3acc720fdec68