Nocturnal Nightmare - The magical movement of M31

[tutting]

Hi all, looking for some guidance on what I've done wrong in my last imaging session.
Background info: equipment used,  Star Adventurer tracker, ED72 scope & D5300 DSLR.
Setup steps: level tripod, polar align (using SharpCap), tracking speed set to star, 90 second exposures

As you can see from the 3 images my target of M31 has drifted across my frame over the course of the session approx. 2hrs (red box is center on all images)

I've used this setup several times and not had this issue before, can somebody give me any info on what might have gone wrong in this session please?

Many thanks.
 

[barbulo]

It seems to me that the Star Adventurer is not tracking properly. Take a close look at the stars and you will see an elongation in the same direction of the M31 drifting.

[DaveS]

Low battery?

RA clutch not fully tightened?