Bluehost - Cronjob设置更改,没有我的干预

I have a shared hosting account on Bluehost. I have set a cron job (of opening a php file on my site) on cPanel that runs every 1 min. It works well initially but when I'm back after a day, I see that the cron job frequency has been changed to something else (every 22 mins, or every 23 mins). I am 100% sure that no one but me and bluehost staff has access to my settings. They claim that they never change a user's settings so this has to be some automated change by linux. Have you ever experienced something like this? What could the reason be?

This is really weird and annoying cause it disrupts my website functionality

Just for future bluehost shared hosting customers:

This is their response:

I spoke to engineers and it is the root server causing time reset. There is no way to fix it on shared server about synch to the server time.

So basically if you have shared hosting, you can't have cron jobs. At least not the ones that run every 1 min.