904 leak...dipstick???

With a new O ring and seated in the trans, the tether on the tube should line up against the bolt hole with minimal effort. If you find you need to force the tube to insert the bolt, the tether could have been bent before. Enough misalignment will cause a new O ring to leak.
For what its worth... My select shaft seal started leaking so I leplaced that. Short time later the front seal started leaking. I wasn't surprised. All of them have the same age.
Good luck with yours