Working fine, tested with Doom and Ultima VI, both on an external sd card. ?♂️
I run the game, load a savegame. Save, load without issues. Go to phone desktop (via home button), launch web browser and Gmail client, then go back to Magic Dosbox. I can still save and load just like before.
This is really puzzling, especially because it’s happening on two devices. Do you perhaps have another sd card to test with?