Recurring error using lmer() function for a linear mixed-effects model in R : I am attempting to run a linear-mixed effects model in R using the lmer() function from the lme4 library and am running into a recurring error.  I am attempting to run the model with two fixed effects: DBS_Electrode (factor w/3 levels) and PostOp_ICA (continuous variable).  I am using (1 | Subject) as the random effect term in which Subject is a factor of 38 levels (38 total subjects).  Below is the line of code I am attempting to run:

LMM.DBS <- lmer(Distal_Lead_Migration ~ DBS_Electrode + PostOp_ICA + (1 | Subject), data = DBS)

I am receiving the recurring error "number of levels of each grouping factor must be < number of observations."  I would appreciate any help, I have tried to navigate this issue myself and have been unsuccessful.