I'm not able to reproduce your issue with the sample data you have provided
# library calls
library(dplyr)
library(tidyr)
# Sample data on a copy/paste friendly format
DS90_prueba <- structure(list(Parametro = c("Aluminio total (Al)", "Arsénico total (As)",
"Cadmio total (Cd)", "Cinc total (Zn)", "Cobre total (Cu)", "Cromo total (Cr)",
"Manganeso total (Mn)", "Níquel total (Ni)", "Plomo total (Pb)",
"Selenio total (Se)"), `Tabla 1` = c(5, 0.5, 0.01, 3, 1, NA,
0.3, 0.2, 0.05, 0.01), `Tabla 2` = c(10, 1, 0.3, 20, 3, NA, 3,
3, 0.5, 0.1), `Tabla 3` = c(1, 0.1, 0.02, 5, 0.1, 2.5, 0.5, 0.5,
0.2, 0.01), `Tabla 4` = c(1, 0.2, 0.02, 5, 1, 2.5, 2, 2, 0.2,
0.01), `Tabla 5` = c(10, 0.5, 0.5, 5, 3, 10, 4, 4, 1, 0.03)), row.names = c(NA,
-10L), class = c("tbl_df", "tbl", "data.frame"))
# Relevant code
DS90_prueba %>%
pivot_longer(`Tabla 1`:`Tabla 5`,
names_to = "Tabla",
values_to = "Valor") %>%
filter(Parametro == "Aluminio total (Al)")
#> # A tibble: 5 x 3
#> Parametro Tabla Valor
#> <chr> <chr> <dbl>
#> 1 Aluminio total (Al) Tabla 1 5
#> 2 Aluminio total (Al) Tabla 2 10
#> 3 Aluminio total (Al) Tabla 3 1
#> 4 Aluminio total (Al) Tabla 4 1
#> 5 Aluminio total (Al) Tabla 5 10
Created on 2020-10-03 by the reprex package (v0.3.0)
Try reinstalling/updating dplyr and tidyr, if the issues persist, share a proper reproducible example (like the one I have posted).