I have the same issue and trying this fix still returns the same "expecting a ds_map" error. (on runtime v2024.4.1.202)
Viewing post in FATAL ERROR while messing with live room instances
I suspect this is somewhat related, I think I've found a smaller issue to do with live room instance ordering.
When reloading a room, the layer order is correct on reload, but it seems the instances within each of those layers get reversed so that instances that should be in front are now behind. Has this been reported? I can dig deeper and send an example if that would be helpful.