Hi Denis Pokotylyuk, this is known issue with 2D FeatureLayer labels at version 64.0 of the 64-bit Firefox browser on macOS. Older versions of Firefox seem to work fine, as well as the latest versions of Chrome and Safari on macOS. All Windows browsers appear to behave fine. We are working to address this for the next release. I do not know of a workaround at this time (other than using a 3D SceneView or a different browser).