All my piano exams have been with LCM, and all passed. Up to grade 6 were over 60 years ago, G5, 7 & 8 over a 12 month period to December 2009.
I don't recall any problems with the 'childhood' exams, but certainly in those exams taken recently I can confirm that the examiners were both fair and helpful. For example, in my G7 I was making such a mess of one of the studies that I stopped and asked if I could start again. He said yes and, I believe, only docked me one mark for that.
They are certainly not seeking 'perfection', more that you understand what you are playing. In fact, I can't recall coming out of any exam thinking 'that piece was perfect'. I'm sure you won't have any problem.