I have been having this problem as well. I contacted the FF people and they could replicate the problem only with a new profile. Old profiles worked as usual. Several other users have reported that the forums they are using that use mlf are having he same problem. mlf works with ie11, edge, chrome etc. but has this bug with FF. I wish someone from mlf would contact the FF admin coders and see if a fix could be worked out between mlf and FF. I like both products but refuse to use the other browsers due to issues with the manufacturers. Thanks to the mlf folks for their product as well.