Was Troughton a bit doddery in his first story as well? I guess if every molecule of my body/personality had just been rewritten I'd be a little out of sorts too...
Did the 4th Doctor arrive pretty much fully formed personality wise? I can't recall...
Troughton was a little jumbled for a little bit, but, not as bad as future Regenerations (And this actually makes sense, because Doctor 1 simply died of old age, he laid down and regenerated, whereas, the rest mostly all died in some kind of Trauma (Two's Regeneration was forced upon him, which seemed to have that same traumatic affect)
Doctor Four, was jumbled, but, not absent from the episode, and not as bad as some others (Three was literally dying and he was helped to Regenerate by another Time Lord who was in the Final Pertwee story)
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?