invalid class “corMatrix” object: 'sd' slot has non-finite entries: lmer() R

I am getting the following error when I run a linear mixed model.

Error in validObject(.Object) : 
  invalid class “corMatrix” object: 'sd' slot has non-finite entries
In addition: Warning message:
In vcov.merMod(object, use.hessian = use.hessian) :
  Computed variance-covariance matrix problem: not a positive definite matrix;
returning NA matrix

I have created a loop that runs through the columns of my data frame and run a LMM for each column. I have run the same process on 2 other data frames and I had no errors. The other data frames have similar properties (i.e contain 0s etc.). I have also tried excluding rows that contain zero values and this has not fixed the error.

Can anyone explain what this error means?

My loop: I am running LMM with likelihood ratio test

uni_HPOS_total1_A = data.frame(metab = character(), beta = double(), pvalue = double(), stringsAsFactors = FALSE)

for (i in 1:length(colnames(HPOS_XCMS_metab_0_new))){
  model0 = lmer(HPOS_XCMS_metab_0_new[, i] ~ (1|technical covariate)  ,
                REML = FALSE, data = HPOS_XCMS_metab_0_covars)
  model1 = lmer(HPOS_XCMS_metab_0_new[, i] ~   (1|technical covariate)   + outcome,
                REML = FALSE, data = HPOS_XCMS_metab_0_covars)
  beta = summary(model1)$coefficients["outcome",1]
  res <- anova(model0, model1)
  pval = res$`Pr(>Chisq)`[2]
  uni_HPOS_total1_A[nrow(uni_HPOS_total1_A) + 1,] = list(colnames(HPOS_XCMS_metab_0)[i], beta, pval)
}

Thanks