They are starting to get on my nerves as well. Every time it takes few days for google to reflect on changes. And they did again. After upgrade, now they complain about the wrong format of startDate and endDate:
Search Console has identified that your site is affected by 4 Events issues:
Top Errors
Errors can prevent your page or feature from appearing in Search results. The following errors were found on your site:
Date/time not in ISO 8601 format in field 'startDate'
Invalid value type for field 'startDate'
Top Warnings
Warnings are suggestions for improvement. Some warnings can enhance your appearance on Search; some might become errors in the future. The following warnings were found on your site:
Invalid value type for field 'endDate'
Date/time not in ISO 8601 format in field 'endDate'
We recommend that you fix these issues when possible to enable the best experience and coverage in Google Search.
I had a look at the HTML of my events page. I presume we are missing T delimiter between date and time part of startdate and endDate
"startDate":"2020-05-0508:00+02:00","endDate":"2020-05-0510:30+02:00"