I think I've found a workaround for crashes, now it occurs much more rarely than before.
1. Use the "storage in the wardrobe/cupboard/pile of rubble" method.
2. Instead of clicking away, drag n' drop the items you wish to duplicate.
3. Have a lot of stuff.
Remember to turn off the trainer as soon you have finished duplicating items.
Works for me, there is a good chance it will work for you as well.
Just tried that didn't work