Ender-3 Pro - PLA mid-layer warping (layer separation) - salvageable?
One hundred percent infill is not necessarily stronger than lower values. By having such a high infill figure, the forces on the model as it cools are magnified and not in a particularly good manner.

Consider that you could use twenty to thirty percent infill to get the strength you require for this application, saving filament and time for the print. You've not noted how many wall layers used, but for increased strength, four to five would make for a very strong model.