lme function for mixed models for dichotomous variables: Singularity in backsolve at level 0, block 1

I am adjusting a fixed effects model considering some covariates. Regarding the specification of the model, two of these covariates are nested and have fixed effects. See that the following error below is happening.

data: https://drive.google.com/file/d/1hKfYpcgAV4gdDPHXv_4EQpiO0Y31_ZVo/view?usp=sharing

library(nlme)
library(lme4)

dados$VarCat=as.factor(dados$VarCat)
dados$VarX5=as.factor(dados$VarX5)
dados$VarX6=as.factor(dados$VarX6)

modelANew <- lme(log(Resp)~log(VarX1)+log(VarX2)+(VarX3)+(VarX4)+VarX5/VarX6 ,random = ~1|VarCat, 
                 dados, method="REML")

Error in MEEM(object, conLin, control$niterEM) : 
  Singularity in backsolve at level 0, block 1

Variable X6 is a dichotomous variable. This seems to me to be interfering with the convergence or estimation of the model. How can I solve?

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