They were thawed and then frozen again
Once you choose to freeze some foods, you should keep them that way because otherwise they may experience burns and lose their proprieties. “Once an item is frozen, it should remain frozen until ready to thaw and cook,” Palafox says.
To avoid thawing food that you are not ready to cook, it is recommended that you divide the food into different bags and then place them in the freezer. For instance, if you have meat, then cut it into small pieces, namely as much as you usually eat, and wrap them separately.
“Foods that partially thaw, then freeze, and then thaw, and then freeze are especially prone to freezer burn,” Lam says.