It’s funny because I recently experienced a very similar issue with the assetManager. I wasn’t using containers but else my method was pretty much the same (using an async function to pass the url and file), disposing of the mesh before adding a new task. The result I got was a dramatic loss of framerate although the model was disposed (and as I said didn’t even use containers).
I wanted to make a PG but left this aside for now, switched to another method suitable for my project without using the assetManager and have no memory leaks and much lower impact on performance while importing the asset.
I will still want to use this method (with containers this time) for loading sets of textures. I fear I will face the same problem. Will be back on it later this week.