I've had to revert a recent engine update to a previous runtime version, as spotted some oddities with collision checking. Lookups seem to be checking incorrect tiles, depending on size/location so seeing some bizarre behaviour.
This does mean the recent custom music track loading, i've had to disable, but everything else should be working ok now.
I'll need to research the engine docs and see what's changed with collisions, or if it's a bug in this recent update.
Sorry for that folks.
Nick