I dual-boot Manjaro and Windows, via Grub and UEFI on a Lenovo Yoga C930, which uses Bitlocker and Secure Boot. I can successfully boot into Manjaro if I disable Secure Boot in BIOS, and I can also boot into Windows if I re-enable Secure Boot in BIOS. For reasons unknown, and seemingly at random, I'll just lose my Linux bootloader. I don't know whether it's getting deleted, or suddenly can't be recognized, or what, but I can't boot from it, and it doesn't show up as an option in BIOS.
I can manage to reinstall Grub by following the instructions on the Wiki, but eventually it will just disappear. What's going on, and how can I prevent this from happening?