"No Symbol information for the file" even when inside the file

Environment data

VS Code version: 1.41.1
Extension version (available under the Extensions sidebar): 2020.1.58038
OS and version: Windows_NT x64 10.018363
Python version (& distribution if applicable, e.g. Anaconda): Python 3.7.0b3
Type of virtual environment used (N/A | venv | virtualenv | conda | ...): N/A
Relevant/affected Python packages and their versions: python-pptx v0.6.18
Jedi or Language Server? (i.e. what is "python.jediEnabled" set to; more info microsoft/vscode-python#3977): false

Expected behaviour

I installed python-pptx and then opened the Presentation.__file__ in it and then chose Go-to Symbol in File, I expect it to list the symbols in that file.

Actual behaviour

But it says: "No symbol information for the file". I've also waited there thinking it might be still loading things but it's permanent and is not showing the symbols. Then I thought it might be because of the kind of deep installation path of my Python (in the local in the appdata, is that deep?) and so copied the file to the root of a drive and now when I reopen it, the option works instantly. Could someone tell me whether it's really my bad Python installation path or something else? I read here that such an issue might be an extension thing so I'm posting this here.

Steps to reproduce:

pip install python-pptx
open the file Presentation.__file__
Hit Ctrl+Shift+O or Click on Go -> Go to Symbol in File
the list is empty and the message there is: "No Symbol information for the file".

Logs

User belongs to experiment group 'ShowPlayIcon - start'
User belongs to experiment group 'DebugAdapterFactory - experiment'
User belongs to experiment group 'PtvsdWheels37 - experiment'
User belongs to experiment group 'UseTerminalToGetActivatedEnvVars - control'
> conda --version
> pyenv root
> python3.7 -c "import sys;print(sys.executable)"
> python3.6 -c "import sys;print(sys.executable)"
> python3 -c "import sys;print(sys.executable)"
> python2 -c "import sys;print(sys.executable)"
> python -c "import sys;print(sys.executable)"
> py -3.7 -c "import sys;print(sys.executable)"
> py -3.6 -c "import sys;print(sys.executable)"
> py -3 -c "import sys;print(sys.executable)"
> py -2 -c "import sys;print(sys.executable)"
> ~\AppData\Local\Programs\Python\Python37\python.exe -c "import sys;print(sys.executable)"
> ~\AppData\Local\Microsoft\WindowsApps\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Microsoft\WindowsApps\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Microsoft\WindowsApps\python3.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Microsoft\WindowsApps\python3.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> C:\ProgramData\Anaconda3\Scripts\conda.exe info --json
Starting Microsoft Python language server.
> (value not set)\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> (value not set)\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> C:\ProgramData\Anaconda3\Scripts\conda.exe env list
> (value not set)\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> (value not set)\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Programs\Python\Python37\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Programs\Python\Python37\python.exe c:\Users\mojta\.vscode\extensions\ms-python.python-2020.1.58038\pythonFiles\interpreterInfo.py
> ~\AppData\Local\Programs\Python\Python37\python.exe -m pip --version
Starting Microsoft Python language server.

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help; turn on source maps to make any tracebacks be useful by running Enable source map support for extension debugging) (I open the console but I really have no idea where to run Enable source map support for extension debugging, it doesn't sound like JavaScript to be entered in the console :/ )

microsoft / python-language-server