Pay run start date changed after saving

We pay the majority of our employees on a monthly basis.  I setup the pay run for June for the period 1/6/24 to 30/6/24 with a payment date of 25/6/24. 

I as halfway through the pay run and saved and closed the pay run so that I didn't lose my entries if the system crashed.

When going back into the pay run, the start date has updated to 31/5/24. I double checked the dates when I started the pay run.  With EOFY I wanted to make sure the dates were correct.

I am sure that this happened yesterday too!  I deleted that pay run and started the re-entry today.

How can I fix this without deleting and restarting the pay run?