If you ever decide to unlock your bootloader, I’d suggest not relocking it until it is known what exactly causes the bricks (and the issue has been fixed). The state of your bootloader also doesn’t impact the security of your data, so it isn’t too big of an issue to just keep it unlocked. I’ve tested some apps known for not working on rooted phones (including banking ones) and all but one worked with minimal setup.
About the bootloader issue: As of now we do not know 
. There should be ways around this issue, but I’m not aware of a 100% safe method.