been through a couple of those on my late 99 zf6
, real easy to change out, no bleeding or anything as its a sealed unit
just an fyi, obviously you found the source and corrected it, which is good, but for future ref. those are also symptoms of bad tranny fluid(dont ask me how i know)
mine(tranny) was replaced a short time ago, i had the same issues, thinking the same, but checked the fluid first, and it was nasty bad
actually called the zf group, which was quite helpful, and with crossed fingers and some serious praying, after i changed the fluid, and flushed 2x im back to good.
still not sure what made the fluid go bad so quick, but keeping an eye on it now, dont wanna drop another 4-5k on something i could avoid
be sure and check your fluids if you dont already!!