Solus OS broken boot

I had a perfectly fine and running Solus OS installation on a 100gb of 1tb hard drive. When I created a partition on the remaining 900gb, boot just vanished. I tried all the things from the internet, regarding the Solus or not. I even don't have the hard drive as a boot option anymore, but I can see the partition and all the files if I boot live CD or other hard disk. **Now the weirdest part:** if I attach the "problematic" hard drive to the computer via. USB enclosure I AM ABLE TO BOOT WITHOUT PROBLEM, but still no luck if attached to SATA, so I suspect there must be some problem with EFI. I tried everything I know and everything I could find on the internet without luck. Note: there were some updates in Solus that might have messed up the boot, but I doubt as I can regularly boot via USB and not via SATA **EDIT:** I remember I followed [this instruction](https://solus-project.com/articles/installation/disks/en) while installing the Solus OS. Boot, swap and main partition are visible via GParted. Boot partition has both **boot** and **esp** flags set. GParted also shows that around 300MB disk usage on boot partition that is 500MB large. I tried the following [boot rescue instruction](https://solus-project.com/articles/troubleshooting/boot-rescue/en) and everything went OK, but the disk still doesn't load. I also tried to use [boot repair tool](https://help.ubuntu.com/community/Boot-Repair) from Live CD with no luck.