AutoCAD 2021 issue of deleting custom dictionaries from previous versions

We have our users reporting an issue with AutoCAD 2021 deleting custom dictionaries from previous versions(steps that can be used to recreate – as reported by a user).

Chances are you have already come across this after looking into AutoCAD 2021.
This issue is currently being addressed by the Engineering. We will keep this post updated once the issue is fixed.

Meanwhile, one workaround is to set the system variable LISPSYS = 0 and restart
AutoCAD 2021, this will prevent AutoCAD from deleting the previous custom dictionaries.

Click here for more on LISPSYS,

Steps to recreate the issue :

1) Open AutoCAD 2020 or an earlier version.
2) Open a blank drawing using the acad.dwt template.
3) Load the visual lisp extended functions using (vl-load-com) in commandline
4) Create a custom dictionary.
     - Type in the following: (vlax-ldata-put "CUSTOM" "KEY" "VALUE")
     - The return value in the command line should be "VALUE".
5) Verify the dictionary key has been set.
     - Type in the following: (vlax-ldata-get "CUSTOM" "KEY")
     - The return value should be "VALUE".
6) Save drawing as DictionaryTest.dwg and close the file.

7) Open DictionaryTest.dwg in AutoCAD 2021 and Load (vl-load-com)
8) Verify the dictionary key: (vlax-ldata-get "CUSTOM" "KEY")
    – The return value is nil.