Fixing non-symetrix sigma matrix

Hello Mixed-Models experts,

I'm trying to fit the following reproducible mediation model called
final. But I get an error saying: ...sigma must be a symmetric
matrix...

Could you please advise how I can possibly fix this error?

Many thanks,
Simon

Reproducible R code:
df <- read.csv("https://raw.githubusercontent.com/fpqq/w/refs/heads/main/t.csv")

library(glmmTMB)
library(mediation)

mediator <- glmmTMB(pic_percent ~ con +
                      (0+con | ID) +
                      (0+con | TRIAL_INDEX),
                    data=df,
        family = beta_family(),
        ziformula = ~1)

outcome <- glmmTMB(acc ~ con + pic_percent +
                      (0+con+pic_percent | Q),
                     data = df,
                   family = binomial())

final <- mediate(mediator, outcome, sims=50,
                    treat="con", mediator="pic_percent")