what is and isn't considered a harmless legal error in a criminal court ??

I spent 4 years in a secure care psychiatric facility after I was forced to plead insanity without my knowledge or consent or ever even setting foot in a court room and given an 8 year intense supervision commitment which is known as "Krol status" in NJ when they were only allowed to give me 3 years (they lied about the degree of one of the counts). I had to argue about this with a public defender who represented me in subsequent commitment hearing for months for him to straighten this out. Years later I was told it was all just a harmless error.
Now sometime after I got charged with a non-violent felony that only carries an 18 month sentence. After I was bullied in pleading guilty before I can see my grand jury minutes (that consisted of 17 pieces of paper after 10 months). The prosecutor reneged on the plea agreement of 18 months and told the judge I should go back to jail for the remainder of 364, I told the judge I had no objection to the prosecutions request, then the judge smiled at me (not an exaggeration) me and gave me 5 years probation. on the second week that I reported to probation some guy tells that it was an illegal probation. So, I go upstairs into the library and find out that they could only give me 18 months-the same length of the possible incarceration. Being that 2 judges, 2 lawyers appointed by the public defenders office, not to mention the prosecutor her self, were all involved in this-can they still consider it "just a harmless error".