Why does ffmpeg cut video at 59:59?

Question

fmpeg

Hello.
Such a problem. I'm trying to convert a lot of videos from webm to mp4 using ffmpeg. It succeeds, but the video over an hour turns into a 59:59 video. Moreover, online converters have the same property.
Tried to convert in pieces. It works, but when merging and saving again, the video is cut off