We're not aware of any brake issues in Vulcan, however, if you're using MSFS 2024 there have been some changes to Parking Brake control assignments in SU3 that could be causing a conflict. See: https://forums.flightsimulator.com/t/parking-brake-cant-toggle-on-off/734585
If brake issues exist in multiple aircraft, that typically points to either a control assignment conflict.
Mark - Just Flight