I've just found the code in PlatformBase.cs. This code could potentially lead to the bugs. And do not correct return device id for WebGL. See code below

            if (Application.platform == RuntimePlatform.PS4 || Application.platform == RuntimePlatform.XboxOne)
            {
#if GS_DONT_USE_PLAYER_PREFS || UNITY_SWITCH
                DeviceId = SystemInfo.deviceUniqueIdentifier.ToString();
#else
                DeviceId = PlayerPrefs.GetString(PLAYER_PREF_DEVICEID_KEY);
                if (DeviceId.Equals(""))
                {
                    DeviceId = System.Guid.NewGuid().ToString();

                    PlayerPrefs.SetString(PLAYER_PREF_DEVICEID_KEY, DeviceId);
                    PlayerPrefs.Save();
                }
#endif
            }
            else
            {
                DeviceId = SystemInfo.deviceUniqueIdentifier.ToString(); //BUG IS HERE
            }

   This code should be replaced to recommended Unity flow for checking the device id with unsupportedIdentifier property. 

https://docs.unity3d.com/ScriptReference/SystemInfo-unsupportedIdentifier.html

And also this code will not works for WebGL because: 

https://issuetracker.unity3d.com/issues/systeminfo-dot-deviceuniqueidentifier-for-webgl-returns-n-slash-a

Ah ok, I've found this place. Thanks.