System Information
Operating system: Windows 10 Business, Build 19041
Graphics card: nVidia RTX 2080 Super

Blender Version
Broken: 2.9x, 3.0
Worked: (works in less complex setups)

Short description of error
I have a bit of a complicated setup and I feel this needs a bit more detailed context, sorry.
I have a blend file that acts as a library of modules (hundreds of collections). To use these modules, I usually link the main scene from the "library" into a new blend file, so I can instance any of the modules.
The modules are set up using a dummy material that needs to be changed after instancing, so I use the "Make Instances Real" command to make the underlying objects accessable. If any of these objects has a material slot linked to the data instead of the object, I have to set that slot to "object" so I can change the material just for this one object, instead of all instances in the scene (of course). I tried to take care of that in the initial library, but sometimes I miss an object or two after creating new modules.

Now, after making instances real, I end up with dozens or hundreds of individual objects that might or might not have a material slot set to "data" - so instead of going "hunting", I select all objects with the dummy material ("Select Linked Material"), hold Alt and change their material slot link to "object".

When I do this, the action goes as expected, but then Blender starts to eat up my RAM until it crashes or becomes unresponsive. Saving, restarting Blender and loading the project restores everything to normal.

The modules in the "library" file consist mostly of meshes, but there are also instances that have been linked in from another external file.

Exact steps for others to reproduce the error
I only noticed this problem appearing after I've been working with the massive module library for months and I failed to reproduce it in less complex setups. I also can't share the files involved in this setup, unfortunately, but I'll try to help anyone who wants to tackle this.