Troy bilt mustang xp transaxle leak

Hi, just joined forum looking for advise. I’m an experienced auto tech I do auto trans and all but as far as mowers never done anything with a hydrostatic trans. Recently purchased a used Troy bilt zero turn and the RH transaxle keeps blowing out the seal on the brake gear shaft. I’ve replaced the seal and topped/purged fluid and it just pushes the seal right out of the casing after a few passes cutting. It’s a oem seal I checked to verify correct size. Wondering if a venting issue is...

Troy bilt mustang xp transaxle leak