Buttons scale keep changing to 0 when I import them to a non-active parent

Hello everybody. I started this project on unity 5.4 and now I updated the editor to the 2017.3 version. In my game I have an inventory, and in the beginning of the game, when the player chooses the "load game" option, the code checks if an item was picked before, and if it was, it is added to the inventory as a child of the inventory grid. The weird thing is that the logic still works, I can see the items on the inspector and on the hierarchy, but for some reason, the items are being instantiated with an X, Y and Z scale of 0, so they're not being shown on the inventory canvas, since they're too small. But when I start the game with the inventory canvas active, the items are instantiated normally with their scales being 1 as they should. This wasn't happening on the 5.4 version, so I was wandering what changed from one version to the other to make this happen, and what can I do to solve it?