Getting this error. Set to backup to /storage/external_SD/TiBU by selecting "Filesystem storage - Ext. SD card". It does say "This folder is not writeable" atthe top ubut it does let me select it. If I select "DocumentProvider storage" it lets me select the TiBU folder but asks me to choose subdirectory. I'm sure I was able to backup to SD before, what am I missing? I have also unchecked "Mount namespace seperation" in SU too.