Currently the onPatches callback does not correctly check the type of received patches.
As you can see below, the code only checks for a type == "move" or 'anything else':

'Anything else' can be problematic when you have a type which emits other type of patches in addition to list-like { type : "splice" } patches, like say... an observable variant of Set - which would emit { type : "values" } patches. These will be partially processed in a wrong way and might even involve exceptions being thrown. When really; they should just be ignored, because the type is incompatible.

The entire patcher also seems to not correctly use 'safe' means of iterating the lists using can-reflect.
It is possible to have a type that implements an iterator (and thus is deemed can.isListLike ) but which is NOT actually fully list-like and which does NOT implement index-based random access accessors.