Here's the skinny. Pokemon crystal version cart. Its original battery is long dead. Friend tried to separate original battery and reuse its tabs with a CR2025 rechargeable battery. In their attempt, it simply would wipe the save when trying it again after unplugging the cart or even simply turning it off and back on. I gave it a try myself with my own soldering tools, as well as scrubbing away the excess solder with some desoldering braid and a fresh application on the battery at both sides, and the parts where the tabs contact the PCB. Currently, the game will save and if I soft-reset, it will come up and restore fine. However, if I unplug, remove the cart, reinsert and power on, it does show the correct time, implying the battery is correctly keeping the RTC going. But trying to load the save gives a "save file is corrupt!" error. What are my options for this? Preferably, nothing I need to buy additional stuff for.