Error when converting object downloaded by pubmedR into a dataframe

[Kingsman-Key]

rm(list = ls()) Sys.setenv(language = "en") query <- "((Pregnant Woman[Title/Abstract] OR Woman, Pregnant[Title/Abstract] OR Women, Pregnant[Title/Abstract] OR Pregnant Women[MeSH Terms] OR maternal[Title/Abstract])AND english[LA] AND Journal Article[PT] AND 2015[PDAT] : 2021[PDAT]) NOT Animals[Mesh]" api_key <- "8cb3ea6eee236216deadd5b5ff6289d2f909" res <- pmQueryTotalCount(query = query, api_key = api_key) res$total_count D1 <- pmApiRequest(query = query, limit = res$total_count, api_key = api_key) M <- pubmedR::pmApi2df(P = D1)
This is the error generated by the last row of code
Error in FUN(X[[i]], ...) : invalid multibyte string 656 In addition: There were 36 warnings (use warnings() to see them)
I attached the list downloaded by pubmedR, it's in the form of Rdata
Thanks a lot if you could help me understand what's happening with my code

[Kingsman-Key]

rm(list = ls())
Sys.setenv(language = "en")
query <- "((Pregnant Woman[Title/Abstract] OR Woman, Pregnant[Title/Abstract] OR Women, Pregnant[Title/Abstract] OR Pregnant Women[MeSH Terms] OR maternal[Title/Abstract])AND english[LA] AND Journal Article[PT] AND 2015[PDAT] : 2021[PDAT]) NOT Animals[Mesh]"
api_key <- "8cb3ea6eee236216deadd5b5ff6289d2f909"
res <- pmQueryTotalCount(query = query, api_key = api_key) res$total_count
D1 <- pmApiRequest(query = query, limit = res$total_count, api_key = api_key) M <- pubmedR::pmApi2df(P = D1)