【DRBL】 has mismatched GPT and MBR partition!!!

Since your /dev/sda has mismatched GPT and MBR partition, and you mention you are sure your disk is only using MBR, you should wipe the GPT table. It's a risk, though.
Backup important data before you continue the following steps. All the data on the disk may be gone if something goes wrong. Therefore be careful.

1. Boot Clonezilla live
2. Enter command line prompt
3. sudo -i
4. sgdisk -z /dev/sda
(Make sure /dev/sda is the disk containing mismatched GPT and MBR partition.)
5. reboot.