Why didn't the Doctor remember encountering the clockwork droids before in his 10th incarnation?

Question

In Deep Breath after seeing droids, he tried to remember seeing these things before but doesn't put it right:

DOCTOR: I've seen this before. I'm missing something.
CLARA: Doctor.
DOCTOR: It's the brand new head, rebooting.
CLARA: Come on.
DOCTOR: I've seen this before.

and also

DOCTOR: SS Marie Antoinette. Out of control repair droids cannibalising human beings. I know that this is familiar, but I just can't seem to place it
DOCTOR: Sister ship of the Madame De Pompadour. No, not getting it.

Why didn't the Doctor remember encountering the clockwork droids before in his 10th incarnation? Did his memories of all his 13 faces' adventures need to recharge?

Answer 1

There are two reasons.

Post-Regenerative Trauma

The Doctor is consistently quite hazy after a regeneration; this confusion is typically chalked up to something called "post-regenerative trauma," and his memory is often affected.

For instance, the Eighth Doctor forgot his entire identity, including his species:

Doctor: I don't know who I am, but I know you know me.

Grace Please go away.

Doctor: Please, you're my only hope.

Grace I'll call security!

Doctor: Do you know who I am?

^{Doctor Who (1996)}

This is also why he's rather manic in Deep Breath, a far cry from the more reserved character of later episodes. Basically, he hasn't quite finished settling in yet.

It was a long time ago

The Doctor doesn't have a perfect memory; he forgets old adventures, just as you or I forget things that happened long ago. The Eleventh Doctor expresses a similar confusion regarding the Great Intelligence, faintly recognizing the name but not recalling their previous confrontations:

Doctor: The Great Intelligence. Rings a bell. The Great Intelligence.

^{Doctor Who 2012 Christmas Special "The Snowmen"}

From the Doctor's perspective, it's been a long time since the SS Madame de Pompadour; it's not unreasonable for his memory of the event to have faded.

Answer 2

As stated by Peter Capaldi on the Doctor Who fan club YouTube, when he first regenerated he was all over the place. He had spent around 1100 years on Trenzalore, if you go by Matt Smith being 904 and at the end of Deep Breath saying 2000; he was also granted a new regeneration cycle, which has never been done, and compared to other regenerations it was a massive one. If you put those 2 together along with the standard fuzziness the Doctor gets from regenerating, it was most probably the whole thing in one.

So along with getting nurse and Clara getting mixed up, assuming it was a 2nd dinosaur, realising the regeneration has gave him a face of a previous human he rescued (remember The Fires of Pompeii), then previous adventures are obviously the bottom of the pile of things he needs to remember.