Henry Winkler is opening up about why his relationship with Tom Hanks is so tense ... and he says repairing the relationship isn't off the table.

In a new interview on "In Depth With Graham Bensinger," Henry recalls getting fired as the director of Tom's movie "Turner & Hooch."

Henry said he felt a bit out of his depth when he took the job, and explained ... "I, at that time being insecure, I talked too much and I gave them direction. I [did] what I thought was my job, and I wanted to do it over again, and apparently that pissed them off."

He said he got sacked not even 2 weeks into filming ... he was devastated and didn't handle the firing well.

When asked where the tension in their relationship came from, Henry responds that he's not sure, considering Tom was a guest star on "Happy Days" before he made it big.

Henry said ... "We did a retrospective of 'Happy Days,' and we wanted 60 seconds of Tom Hanks in his episode, and we did not get permission for that."

As far as his takeaway ... Henry says he's "still working" on his perspective about the whole thing.

But peep the clip ... it seems like Henry's open to putting those not-so-happy days behind them.