In TWRP, go to Wipe > Advanced Wipe . Select Dalvik, System, Data, and Cache.
We tested a 2-year-old OPPO A5s (4GB/64GB variant) over 48 hours. oppo a5s custom rom download work
Installing a custom ROM on your Oppo A5s (CPH1909) Go to product viewer dialog for this item. In TWRP, go to Wipe > Advanced Wipe
file of the custom ROM you downloaded and "Swipe to Confirm Flash". Flash GApps (Optional) oppo a5s custom rom download work
Do not use generic TWRP. Use the specific twrp_cph1909_3.7.0.img .