RPC error re:SFC module item limit

I was creating an SFC and copying steps/transitions, when I suddenly got an RPC unavailable error.  It basically crashes the module and Explorer. Close explorer, start over. But, I can't copy and paste new steps.

Have narrowed it down to some sort of limit on my items. I also have function blocks doing calculations in the background and for every one item (function block, step, or transition) that I delete I can copy and paste a new item.  I am not at the limit for steps that I've seen before (I believe 255). And that gave me a far different error.

I'm not sure what the .. is going on. But, this is beyond strange.

Thanks