Small k on my antenna

[NinoZore]

hello guys i have a problem ,my bluetooth program only work on esp32 Dev kit who has an small k on the antenna

IMG_20230217_094057.jpg (493.59 KiB) Viewed 2260 times

and dont work for esp who dont has this small letter ,i dont understand what this small letter mean ?!? Version of the esp32 ? low quality copy ? i dont understand !
Thanks for your help
Nino =)