### Godot version

v4.0.beta14.official [28a24639c]

### System information

Windows 10, OpenGL

### Issue description

Vulkan and Mobile:
![Godot_v4 0-beta14_win64_kEcRNiMfNJ](https://user-images.githubusercontent.com/7782218/213967627-8e8755d9-2fe2-43b3-b197-f9f2840b7580.gif)

OpenGL:
![Godot_v4 0-beta14_win64_MQ233TZuPq](https://user-images.githubusercontent.com/7782218/213967651-ae463a6f-c867-4312-bdf1-525e1d7def01.gif)

At first I thought it was related to `set_buffer()`, but it turned out that `set_instance_*` also work incorrectly.
Probably the custom information is also set incorrectly, but I haven't checked it yet.

### Steps to reproduce

* Open MRP
* In the editor, select `MeshInstance3D` node and change the `Count` property
* -- or --
* Start the project and move the slider

You can also switch the renderer to Vulkan and compare.

### Minimal reproduction project

[set_buffer().zip](https://github.com/godotengine/godot/files/10476834/set_buffer.zip)

if (multimesh->data_cache.size() > 0 || multimesh->instances == 0) {
		return; 
	}
	ERR_FAIL_COND(multimesh->data_cache.size() > 0);
	
	
	multimesh->data_cache.resize(multimesh->instances * multimesh->stride_cache);
	{
		float *w = multimesh->data_cache.ptrw();
		if (multimesh->buffer_set) {
			Vector<uint8_t> buffer = Utilities::buffer_get_data(GL_ARRAY_BUFFER, multimesh->buffer, multimesh->instances * multimesh->stride_cache * sizeof(float));
			{
				const uint8_t *r = buffer.ptr();
				memcpy(w, r, buffer.size());
			}
		} else {
			memset(w, 0, (size_t)multimesh->instances * multimesh->stride_cache * sizeof(float));
		}
	}
	uint32_t data_cache_dirty_region_count = (multimesh->instances - 1) / MULTIMESH_DIRTY_REGION_SIZE + 1;
	multimesh->data_cache_dirty_regions = memnew_arr(bool, data_cache_dirty_region_count);
	for (uint32_t i = 0; i < data_cache_dirty_region_count; i++) {
		multimesh->data_cache_dirty_regions[i] = false;
	}
	multimesh->data_cache_used_dirty_regions = 0;
}
void MeshStorage::_multimesh_mark_dirty(MultiMesh *multimesh, int p_index, bool p_aabb) {