Apart from that, there is a long list of what might have caused the leaking:
Abrasion from dirt or dried media on stem and sealings
Too hot/cold media or temperature variations
Pipe/pipe parts or valve/parts moved by unproper support and fastening
Corrosion
Unsuitable media
Uncorrect handling/closing/opening force giving mechanical damage
Mechanical parts and sealings outside manufacturing tolerance
..... and so on
When you do not know anything of a failure then you list up all possible causes, then you start to check and eliminate.
A broken pipe upstream repaired or unclean water source could put anything into the pipe from silt, dirt, gravel, metal filings up to twist. It does not have to be anything of this.
'Damaged sealing' cover most of this but explain nothing.