Beta image has no correct page alignment. When flashing the last image recalbox.2019-02-23-beta.rpi3.img.xz to an 256 GB micro SD card, I'll get the following partitions:

Disk /dev/mmcblk0: 238.5 GiB, 256087425024 bytes, 500170752 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x4b10cc2b

Device Boot Start End Sectors Size Id Type
/dev/mmcblk0p1 1 131072 131072 64M c W95 FAT32 (LBA)
/dev/mmcblk0p2 131073 4325376 4194304 2G 83 Linux
/dev/mmcblk0p3 4325377 500170751 495845375 236.4G 83 Linux

It should look like this:

/dev/mmcblk0p1 1 131071 131071 63M c W95 FAT32 (LBA)
/dev/mmcblk0p2 131072 4325375 4194304 2G 83 Linux
/dev/mmcblk0p3 4325376 500170751 495845376 236,4G 83 Linux

so that micro-SD card formatting for performance and wear-leveling is more optimal.