My FinePix S2980 resets time and date to 00:00 01.01.2000 whenever it is switched off and the SD card and/or batteries are...

This fault is apparently unsolvable and cannot be repaired. There is no internal battery inside a FinePix camera, just a small capacitor soldered to the main board. Whether from old age (S2980 released 2012) or age + use related, the capacitor eventually fails, so you have much less time to change batteries (typically 10-15 seconds) or remove the SD-card. A workaround solution is swapping the batteries extremely fast or removing the SD card fast, means that the battery chamber cover is only open for a matter of seconds before being closed again.