Brush Opacity and Flow not Resetting

Recently I have been having a peculiar issue with some Photoshop brushes with the Opacity and Flow settings not reverting to their original levels when changing between brushes. While this isn't a major issue, it is incredibly frustrating!

Example: I'm using a hard brush to do some outlining, both opacity and flow are at 100%. I change to another brush, an imported one, where the flow and opacity are at 25% and the airbrush-style is on. But when I go back to the hard brush, the airbrush-style is the only setting that changes, the opacity and flow don't revert to 100%.

This seemed to only be an issue when using the General Brushes under the PS default brush set, with all the brushes being stuck at 100% despite the preset being low opacity/flow.

I have tried a number of things to solve this issue, but as of yet, none of them have worked:

• Removing all imported brushes and appending default brushes (the General Brushes all remain at 100% Opactiy/Flow)
• Resetting all locked Settings under Brush Settings (which did remove an error with the Pen Pressure, but the Opacity/Flow issue remains)
• Duplicating and remaking the General Brushes I use the most as new brushes - these brushes keep their Opacity and Flow settings when I switch between brushes, but other brushes now refuse to revert where they had done so before
• Resetting Photoshop preferences

I am using Photoshop 2020 on a macOS High Sierra (version 10.13.6) and am unable to update my version of Photoshop due to incompatability. I hope I have made things clear here, and I hope someone might be able to help! Thanks!