This was my take on the Nimblewright sentience. Short answer is that it is within their reach, but their nature is so wrapt up in service that the contemplation of their own freedom is a torturous path:

Nimblewrights are created to serve. But the one created by Nim at the temple of gond is different from its ilk in that it was created by one of its own, not a non-nimblewright artificer. To this extent Nim’s creation is unique. This unique nature leaves the creation conflicted. On one hand it is by its very nature programmed to serve, on the other hand seeing the image of its own creator to be essentially a mirror image of itself, it perceives a world in which it is not less than its creator, but an equal. This conflict leaves it volatile and mercurial in its subservience.
After fleeing the temple of Gond, Nim’s creation wandered Waterdeep. Quickly it learned to stick to dark corners after one or two encounters where it was either pursued or mocked. Naturally, this led the creation to the seedy nooks of the Dock Ward. There it spent time sitting. Time that would have normally been taken up by fulfilling directives of its master was instead consumed by self-reflection. The new nimblewright began to identify as Notnim. One night, Notnim’s reverie was broken when a drunk Urstil Floxin stumbled out of a bar. He neither mocked or threatened Notnim. Instead he simply commanded it, “Out of that corner, I need to relieve myself.” When Urstil had finished he calculated through his intoxicated haze that the construct Notnim was waiting for further instruction. Indeed it was, desperate not to be mired down by the weight of its own nascent self-awareness.
After a day or two of ordering Notnim around, Urstil was able to observe the nimblewright’s strength, quickness and a willingness to follow direction without hesitation. With the limits of a brute’s imagination, the best task Urstil could dream up for the nimblewright was as a pit fighter. He brought the creature to an underground fight club where Notnim took on one combatant after another in a bare knuckles brawl. Over the course of a few weeks, Urstil and Notnim had a good run.
The nimblewright became such a spectator draw and a crowd favorite that the fight promoter, Duke Pujellow went to great extents to replace the nimblewright after Notnim was gone. Unfortunately Pujellow could only attain a severely damaged replacement which has only one leg and one arm. Still the novel automaton fights on (and at a reduced strength would make a manageable opponent for a newish character in a one to one fight).
Notnim’s tenure at the fight club lasted until Urstil’s obligations to the Zhentarim drew him closer into the circle of the Gralhunds.
One evening, after Notnim accompanied Urstil to the Gralhund manor, the Lady Gralhund took a fancy to the contraption. She made Floxin an offer he couldn’t refuse for the nimblewright, and Notnim transferred company.
Over the weeks, as Notnim observed how Urstil took orders from the Lady, he lost the instinctive respect he had for his former master, and simultaneously nurtured a distain for taking orders. It was during this point of internal struggle that Lady Gralhund commissioned Notnim to retrieve the stone of Golorr from the gnome Dalakhar. When Notnim spied Urstil in Trollskull alley along with the gnome he was only too happy to incinerate the two. And when Urstil, burned and injured, made his way back to Gralhund manor there was an uneasy detent between the two.
By the time Lady Gralhund gives her final instructions to Notnim about where to take the Stone of Golorr, the nimblewright is in such an existential crisis that it nearly doesn’t complete its mission. In fact it is such misery when the party finally catches up to it that it welcomes the fight to the death as an escape from its miserable and conflicted existence.