Error with vars.to.regress: "contrasts can be applied only to factors with 2 or more levels"

[yesitsjess]

When running:
soup_obj <- SCTransform(soup_obj, vars.to.regress="Sex")

I get the error:

Regressing out Sex
Error in `contrasts<-`(`*tmp*`, value = contr.funs[1 + isOF[nn]]) : 
  contrasts can be applied only to factors with 2 or more levels

But my variable "Sex" is a factor with two levels:

> table(soup_obj$Sex)
  Male Female 
205006  49637 
> levels(soup_obj$Sex)
[1] "Male"   "Female"

Seurat_5.0.3

[ashipde]

I am facing the exact issue (Seurat 5.0.3)

> ce
An object of class Seurat 
13336 features across 50032 samples within 1 assay 
Active assay: RNA (13336 features, 0 variable features)
 12 layers present: counts.nf1, counts.om1, counts.of2, ...

> ce <- SCTransform(cv, vars.to.regress='Batch', verbose=FALSE)
Error in `contrasts<-`(`*tmp*`, value = contr.funs[1 + isOF[nn]]) : 
  contrasts can be applied only to factors with 2 or more levels

> str(ce$Batch)
 Factor w/ 2 levels "A","B": 1 1 1 1 1 1 1 1 1 1 ...
 - attr(*, "names")= chr [1:50032] "om1_TACTGCCCAACCACGC-1 ...

> table(ce$Batch)

    A     B 
40787  9245