BUG: Comms sites, all day event. ICS generation incorrect

Here is a bug I reported to MSFT at Ignite. ICS files generated for all day events are incorrect.

Add an event to a communcation site, make it all day, save, then click 'add to my calendar'. This generates a correct ICS start and end date.

DTSTART;VALUE=DATE:20190417
DTEND;VALUE=DATE:20190418

Then goto see all events, or goto the comm site home page, scroll to the events, find the event and click add to 'my calendar', this generates an incorrect ICS and adds an additional day.

DTSTART;VALUE=DATE:20190417
DTEND;VALUE=DATE:20190419

the ICS files which are generated are different depending on how you view the event, when the event is opened and the ICS is created it is correct. When all events are viewed and the ICS is created an additional day is added. 

please fix.