R data wrangling do not do the function in the whole dataset

I am preparing a dataset for futher analysis. For this I do a timeshift -days(60) and write the result in a new column. Not difficult normally, but the computer is not doing it completly. A few rows where not calculated.

df$acquisition_time=as.POSIXct(df$acquisition_time, format = "%Y-%m-%d %H:%M:%OS")
df$acqui_timeshift <- df$acquisition_time - days(60)

Here I put a screenshot where you see the problem: enter image description here

the "NA" in the corner continues further. The dataset is 1,3 Million rows. So maybe the computerpower is not enough? There is no ERROR: or WARNING: from R

it would be nice if someone can help me with this strange problem!

Thanks a lot!

Best, Christian

    data<- structure(list(ani_id_year = c("982_year2019", "982_year2019", 
"985_yearNA", "996_yearNA"), month = c("02", "02", "05", "05"
), year = c(2020, 2020, 2018, 2018), year_ts = c(2019, 2019, 
NA, NA), acquisition_time = structure(c(1581310879, 1581782462, 
1527120030, 1527120052), class = c("POSIXct", "POSIXt"), tzone = ""), 
    day = c("02-10", "02-15", "05-24", "05-24"), x = c(382992.722829081, 
    384653.805434133, 387585.792076463, 388305.553482353), y = c(5419798.49669287, 
    5420068.44700148, 5411757.45423474, 5401584.90172328), groupid = c(3L, 
    3L, 3L, 2L), name = c(982L, 982L, 985L, 996L), name_echte = c("Tana", 
    "Tana", "Zita", "Berta"), nr = c(1351995L, 1352125L, 
    1370437L, 1278038L)), row.names = c(1256187L, 1256317L, 1281322L, 
1343545L), class = "data.frame")

sorry I really do not know how to add this here, I used dpud() to get the code..