30 min lag on my booking ranges

Hello, I have a problem on my booking page. I could book slots from 2 am to 8.30 am, 10.30 am, 1.30 pm and 3.30 pm. Recently, I can only book at 9 am, 11 am and 4 pm. Everything is delayed by 30 minutes. I tried to change the interval and redo my programming tracks but without success. Have you had the case as well and if so, do you have a solution? Thank you.