.ics meeting invite either does not go into Calendar when clicked or goes in at the wrong time

Occasionally I click on an ics meeting invite in mail and Calendar opens but the invite does not appear or the entry goes into Calendar at the local UK and not the correct time to reflect the timezone difference. Strangly if I click and drag the ics file from the email to Calendar it goes into the calendar every time and at the correct time to reflect the timezone difference.

For further clarity the invite also shows the wrong time on my iPad and iCloud.com

This is clearly a bug but at least I've found a way around it.