# Error fitting random slopes with glmmPQL

I am currently trying to fit a GLM to to describe the following data with both random slopes and intercepts:

The following code with no random slope works:

PQL <- glmmPQL(TorqueT ~ twist, random = ~ 1| BrainID, family = gaussian(link = "log"), data = Cplane)

summary(PQL)


And provides the appropriate output however when I attempt to incorporate random slopes with the following code:

PQL <- glmmPQL(TorqueT ~ twist, random = ~ twist| BrainID, family = gaussian(link = "log"), data = Cplane)


iteration 1

iteration 2

Error in chol.default((value + t(value))/2) : the leading minor of order 2 is not positive definite