Regarding active camera : I have set the MapCamera as the Camera for the Map in the inspector and never change this.

And for second moment : yes, I agree it is better, though mine version works because I have line ( "if (mapCamera.orthographicSize > maxOS) mapCamera.orthographicSize = maxOS;".

Typically, chaotic marker movement occurs when you have a map size not equal to N * 256. So first of all, check the size of the map.

Not relevant to your question, but:

The first moment that I see here (actually I do not see, but should have seen) is that you change the active camera, but do not set this camera for the map. This can cause unexpected behaviors.
http://infinity-code.com/doxygen/online … 0f5f0e3b76

The second moment is mapCamera.orthographicSize == maxOS.
https://www.codeproject.com/Articles/38 … -and-relat
It should be something like: Math.Abs (mapCamera.orthographicSize - maxOS) <float.Epsilon.

 playerMarker = OnlineMapsTileSetControl.instance.AddMarker3D(position, playerPrefab); 

and I use player camera as the main one. Then at some point I switch to the map view disabling player camera and enabling map camera

     void ActivateMapCamera ()
    {
        playerCamera.depth = 0;
        playerCamera.enabled = false;
        playerCamera.gameObject.SetActive (false);
        initialZoom = OnlineMaps.instance.zoom;
        mapCamera.gameObject.SetActive (true);
        mapCamera.enabled = true;
        mapCamera.depth = 1;
    }

then in script on the mapCamera I have this update function:

    void Update ()
    {
        if (mapControlDisabled)
        {
            if (Input.touchCount == 2)
            {
                OnlineMapsTileSetControl tileSetControl = OnlineMapsTileSetControl.instance;
                tileSetControl.allowUserControl = false;
                Zoom ();
            }
            if (Input.touchCount < 2)
            {
                OnlineMapsTileSetControl tileSetControl = OnlineMapsTileSetControl.instance;
                tileSetControl.allowUserControl = true;
            }
        }
    }

where Zoom() is function which changes mapCamera.orthographicSize. And it contains if-statement which checks if we have zoomed out enough

    void Zoom ()
    {
                ...
        if (mapCamera.orthographicSize == maxOS)
        {
            OnlineMapsTileSetControl tileSetControl = OnlineMapsTileSetControl.instance;
            tileSetControl.allowUserControl = true;
            tileSetControl.allowZoom = true;

            mapControlDisabled = false;
        }
        
        // Change player size to increase visibility on the map
        playerMarker.scale = LerpPlayerScale();
    }

and thats when problem starts : player postion starts rapidly changing (swapping between two positions: actual one and the wrong one) and further map is zoomed out further apart these positions are. Interesting moment that if I remove (comment) whole if-statement then no problems arise, but I need the functionality to change map zoom in comfortable for the user way. I hope I can find help here.

P.S. It is code that was written on the 2.5 version of the Online Maps, but I has updated it to the newest version atm which is 3.5 hoping it would fix the problem but no it didn't.