Is that 37 hours, 50 minutes and 55 seconds? See the FAQ: How to do a minimal reproducible example reprex for beginners for how to post questions that provide sufficient information to reproduce the problem.
So, 2 files convert 37:30:55 to "37:30:55" What do the other 10 convert it to? What typeof() do you want it to be? If it's a duration, see the {lubridate} package and follow the link there to the explainer on dates and times in R.