"Attempt to apply non-function" error when trying to write.csv - r

Question

I'm just trying to export my data using write.csv like you'd expect
write.csv(df, "df.csv")
and I'm getting this error:
"Error in app$vspace(new_style$`margin-top` %||% 0) : attempt to apply non-function."
I'm not sure how to troubleshoot this/solve the issue! I double checked that my data is a standard class (it's a data.frame), but beyond that I'm at a loss because it looks like every other data.frame I've ever (successfully) exported. I'm not an experienced error-reader, but if it's helpful, the top line of the traceback is this:
clii__container_start(app, "span", class = funname)
I also did all the basics like quitting and restarting my R session, moving my working directory around, and checking if other data.frames can export -- they can, it's just this one that's stuck.
Here's the output for sessionInfo():
> sessionInfo()
R version 4.1.0 (2021-05-18)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 22000)
Matrix products: default
locale:
[1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] fansi_0.4.2 assertthat_0.2.1 utf8_1.2.1 crayon_1.5.1 dplyr_1.0.8 R6_2.5.1
[7] DBI_1.1.2 lifecycle_1.0.1 magrittr_2.0.1 pillar_1.7.0 rlang_1.0.2 cli_3.2.0
[13] rstudioapi_0.13 remotes_2.4.2 vctrs_0.3.8 generics_0.1.2 ellipsis_0.3.2 tools_4.1.0
[19] glue_1.4.2 purrr_0.3.4 xfun_0.30 compiler_4.1.0 pkgconfig_2.0.3 knitr_1.39
[25] tidyselect_1.1.2 tibble_3.1.2
and for rstudioapi::getVersion()
> rstudioapi::getVersion()
[1] ‘1.4.1106’