[Data Bug] Multiple duplicate GSIS Id entries

[TheMathNinja]

Describe the data bug
10 different Player ID maps are missing because they were overwritten with duplicates of other players.

** Which file is having trouble?**
library(tidyverse)
library(nflreadr)

ffids <- nflreadr::load_ff_playerids()

ffids %>%
filter(!is.na(gsis_id), gsis_id != "", !is.na(mfl_id), mfl_id != "") %>%
count(gsis_id) %>%
filter(n > 1) %>%
arrange(desc(n)) %>%
view()

Expected data
This particular df should be empty, but it shows 10 different GSIS Id's being duplicated across different players as identified by MFL. It looks like this duplication happens for every other row too. So an MFL ID is getting attached to a wrong player and duplicating that player across most/all rows in this df.

Issue #42 is one of these.