I’m trying to use bam() and method=”fREML” to speed up my analyses.

mode11 <- bam(Met1 ~ s(Timepoint, k=7) + s(Timepoint, by=subject, k=7) + s(subject, bs="re"), data=df, method="REML")

model2 <- bam(Met1 ~ s(Timepoint, k=7) + s(Timepoint, by=subject, k=7, m=1) + s(subject, bs="re"), data=df, method="REML")

I noticed the models above run, but when I try and get a summary for model2, I get the following error

Error in h(simpleError(msg, call)) : 
 error in evaluating the argument 'x' in selecting a method for function 'chol': non-conformable arrays

Why might this be (m=1 is affecting it, but not sure why the above error)? A summary of a gam() with m=1 works fine.