yes that is normal behavior. You can adjust the texture page size if you want in the gms settings. GM only has so much space to fit sprites per texture page. When the texture page is filled up then GM will start adding sprites to a new texture page. In 2d this is fine, but in 3D it begins to cause issues when trying to swap texture pages for 1 model, thus giving weird results. You should always try to keep things separated if possible, especially if you have bigger sprites.