Repeating a clip multiple times in AE differs from repeating a clip in premiere?

[avpromedia]

I have a loopable animated background clip. I use AE's interpret footage to repeat this clip.

Premiere does not have this feature so I make many copies and put them one next to another.

Oddly, when I compare the two methods of looping, they drift apart gradually over time.

Any idea why?

[Steve Griffiths]

To be sure that nothing weird is going on I took a 1 second clip into AE, interpreted it to loop 10 times and then rendered, took that to Premiere and compared to the original clip duplicated 10 times in a Premiere Sequence and compared to the render from AE. 

Exactly the same duration.

Could it be either in After Effects or Premiere the clips are being interpreted at different frame rates? If for instance this is a stock animated background - what was it's original frame rate and is it being interpreted the same in both applications.