Popover buttons normally have a toggle state. click on a button and the popover is displayed. click the button a second time and the popover is closed.
For some reason I have two popovers that are not doing that. On the second click they close and then re-open. I have the debugger on to see if there are any scripts being triggered but I can't see any actions occurring.
Are there any known reasons for a popover re-opening instead of closing?
I have not ran into this issue myself but I have had odd issues form time to time pop up and at times closing the FileMaker or even at times restarting the system solves it. It is worth a try if you have not done so already.
Interesting.
It's an app running on Claris FileMaker Cloud. I'll check the logs to see when it is stopped/started.
check the tab order
I'll follow that up.
Have a read of this thread I posted a couple of years ago on TechNet, and the very help full response:
https://community.claris.com/en/s/question/0D53w00005OlXbmCAF/hard-to-explain-popover-button-behaviour
It details a specific button setup,. but if you are using anything like that it may help you.
That post describes exactlly the same situation! 
I have placed two fields above the popover, both are locked on browse mode. Iām doing that instead of labeling the popover to provide access to the fields in find mode.
I had two popovers displaying this behaviour. One would only display the behaviour occasionally. I checked and there was an overlap from the field beside it. I'm guessing that I was clicking the field occasionally.