I also had the issue of not being able to encrypt my phone after changing to Fairphone Open OS.
My solution was, to resize the partition. Essentially only 16 KB need to be empty at the end of the partition.
That means for a partition size of 6798331 * 4KB blocks, the partition needs to be resized to 6798327 * 4KB blocks.
One option, using the adb shell:
- Boot into recovery
- Unmount data
- e2fsck -y -f /dev/block/mmcblk0p20
- resize2fs /dev/block/mmcblk0p20 6798327
Or, even simpler:
- Boot into recovery
- Select ‘Wipe’
- Select ‘Advanced Wipe’
- Select data partition
- Select ‘Resize’
This automatically resizes the partition to the correct number of 4KB blocks.