This unit's hydro uses a cam brake that is internal to the transaxles. Look where brake linkage connects to the transaxle brake lever. Now make a mark across the shaft and lever connection point. Activate or de-activate the braking. Does the marks stay line up but move in unison? IF not then union is strip out: otherwise if things are moving as the should you have an internal problem with the transaxle.
Items 32 and 31 is the lever and shaft. Item 30 is the brake pawl inside the transaxle. Item 40 is the seal.
View attachment 54339