Thanks ChillyWilly I appreciate you looking into it for me.
I have flashed the v7 core to my NEO Myth now but it has not solved this problem though.
Does the saving process depend on the battery in either cart even if using reset to get back to the menu? I was just wondering if it could be something as simple as a dead battery.
Some settings are saved in the sram on the GBA cart. Not sure that would affect game save handling though, just the browser settings. I still need to look at it... I'm having trouble getting caught up with work after being sick last week or I'd have that done by now.
EDIT: Okay, checked the latest menu and save memory seems to save fine. Can you be more specific about what is not working?
Some points to make that were made a while back, but newer folks might not know...
1 - The save memory in the Myth uses a high-capacity capacitor rather than a battery. As such, it doesn't hold the save memory very long. The type of N64 cart plugged into the back of the Myth determines how fast the capacitor drains - some carts were found to drain the capacitor in less than a minute. As such, if you turn the N64 OFF and let it sit, the save memory will go dead after an unknown, but relatively short, period of time.
2 - The menu saves the save memory to SD when you boot the menu. Therefore, if you turn off the N64, wait until the save memory loses power, then turn it on, there will be nothing to save since it was lost due to the loss of power. To save the save memory intact, you need to reboot the menu before the save memory goes invalid. In general, always reset to the menu after playing a game, THEN turn off the power. That will insure the save memory is saved without loss.
3 - There is a write protect slide switch on the SD card. Make sure it is towards the connector edge to allow writing to the SD card.
4 - Many games don't use save memory, they use the mempak in the controller. To determine if a game uses save memory, press Z in the browser to see the cart options, one of which tells you if and what kind of save memory a game is known to use. Note, this data comes from a database of known games. If you are using homebrew, it won't know if the game uses save memory or not. In that case, consult the homebrew docs.
5 - If a game uses save memory, when you reboot to the menu, the save memory is saved to a file in "/menu/n64/save/name-of-cart.extension". The extension is set according to the type of save memory, being one of the following: .eep for eeprom, .sra for sram, and .fla for flash memory.