Not nearly enough info for anyone to do anything but make blind guesses.
Stop calling them hards. Use HDD for Hard Disk Drive or SSD for Solid State Drive so that everyone is speaking the same language.
List your MacOS and version, whether your MBP has an HDD, SSD or Fusion and the size. Does your MBP have a Retina screen or no — yes, it makes a difference.
How are you hooking up your BIAB drive and what version of BIAB do you have?
Are you using and disk utilities? If so, stop — they don't do any good but it's helpful to know.
I am an experienced Mac tech.
I’m not not home now but here is the info I known right now:
1.I am using OSX high Sierra
2. My MacBook Pro uses flash storage and has 1TB of memory. No idea what that means but it’s what Apple’s website shows as the specs for a mid 2014 MacBook Pro
3. My Mac does have a retina screen
4. My 2020 Band in a Box external drive is usually hooked into a four usb hub
5. I’ve really only use disk utilities to reconfigure a flash drive to work on my MacBook Pro to use for DJing. I have tried using disk utilities as I read online to try that as an option. I’ve never went through with it.
Here is what is important to know. A few months ago, my MacBook Pro was overdue for a battery replacement otherwise the computer might have exploded. When I took it to get the battery replaced, the had to reinstall the operating system which forced them to wipe everything off the Mac and store it on an external drive. That drive worked for a while until one day, I got a notice on my Mac that the drive could not be repaired which caused my drive to become read only. No files are able to be deleted or stored in it at all as of now. My BIAB drive was working fine the entire time unlit the day I posted this issue on the form. Both of those drives do not show up on my Mac as being connected sometimes when I connect them into the hub and the don’t show the drive icon when I open the finder app. However, I have a different WD drive that works perfectly reading, writing and storing files. Anyways, that’s all I know. I’ll give you more info when I am back home.