It seems like your SD card may be problematic.
Some SD cards are not genuine or have a lower capacity than advertised. Some simply fail over time.
Symptoms of SD cards not working correctly are:
- Read-only behaviour, or changes made not persisting
- A filesystem corruption error
Symptoms of counterfeit SD cards are:
- Writing works until a certain filesystem size is reached, thereafter, writes seem to cause issues where existing data is lost or newly written data is not preserved.
- SD card fails after a short amount of time.
Counterfeit cards are usually found on Amazon and eBay.
SD cards have a limited lifespan. I recommend you change SD card and suspect that issues will no longer persist with a good card. If you would like to be a good quality SD card purpose manufactured for OSMC, then you can find one in the Store.