My sister has spoken to me before about a 'bedding down' period that happens as the brain properly absorbs new information and starts changing behaviour. Obviously, when the brain gets injured, bedding down can take longer. Accordingly, the times of "little change" can just be times of bedding down. Further gains will happen after the ones already made are bedded down.
In my balance example, the bedding down of gains came as I slowly realised that a lack of core strength in my trunk was contributing to my poor balance. What was required to help that was sticking with exercises that improved that strength. The 'bedding down' happened as I realised one cause of my problems and then set about working on specifically on that.
The bedding down of gains makes it dangerous to write off the possibility of more changes just because changes slow down. There is nearly always more scope to recovery, there is always reason to think about how to recover!
Cheers,