Apparently they were unhappy because of linguistic problems! The present day Egyptian bishops
Please note that it was not only the Egyptians who initially resisted the Tome of Leo, and thus we can infer were probably unhappy with it, even at the Council of Chalcedon. They were accompanied by the Palestinian and Illyrian bishops.
While the Palestinian and Illyrian bishops did approve the Tome after some novel orthodoxizing of its substance, it should be quite clear even from their later comments regarding it that they still weren't happy about it. For all we know there may have been even more than these three groups who were not "happy about it", per say, but were towing the line and signing onto whatever was put in front of them as the hypocritical bishops of that time were often inclined to do.
Finally, the 1500 year old Anti-Chalcedonian tradition which has for most of its time explicitly resisted Chalcedon on doctrinal grounds should make it quite clear that it was not mere linguistic problems.
The present day Egyptian bishops are quite happy with it and have officially declared, in union with the Vatican, that their previous problems were only linguistic misunderstandings between them.
It is true that some bishops in the OO churches are now advocating the idea that there was not true doctrinal difference between the two camps. Whether they represent the majority, I do not know.
It is true that the Egyptian bishops officially recognized the Agreed Statements in synodical discussion. Again, whether they did this because all were individually convinced that this was true, or they did this out of trust for their head, or they did it out of cowardice, I do not know.
However, the same bishops will in the same breath claim that the Tome of Leo was nonetheless "Nestorianizing" or "Nestorianesque", so whether they are actually happy about it, it cannot be said.
Now, so they proclaim, miaphysitism and dyophysitism are one and same.
I've said it a number of times before and I will say it again, the cause of our division is not simply "miaphysitism vs. dyophysitism".