Perhaps Auto Explode gets turned off in Large Assembly mode? If so, you could try raising the limit for Large Assembly mode to more parts than you have in your assembly.
Of course, one reason for turning off Auto Explode in large assemblies might be that it doesn't work very well!
I don't remember when it was taken back but it it NOT available now
The last time I remember auto-explode was about 2001, or so.
It never really worked very well then, but I have occasionally wanted it back for quick and dirty drawings. Sometimes the boss just wants a "picture" showing all the individual parts and a BOM.
The options for making an exploded view have improved so much since then that I don't really miss it too much though. In my experience exploded views require enough "fine tuning" to look good, and clearly show the important things (whatever they happen to be), that I can't imagine that any kind of automated exploding would produce really useful results. Maybe a good starting point but not much more.