I believe the bug is in https://github.com/tidyverse/dbplyr/blob/main/R/backend-oracle.R line 120:

Should look more like this https://github.com/r-dbi/odbc/blob/74ad62c275b1c95a70814707901bdafd8fc2d2b6/R/db.R#L32 line 15:

The effect of this is that anything with temporary = TRUE (e.g. copy_to or compute will result in an empty temporary table. Using {odbc} to connect.