I do not know your environment, Scott. But is your imported calendar part of your (Exchange) account which will be synced to GW?

Mobile devices can host a lot of "local" information like calendars, address books, ... which will stay local or use another synchronization path.

Btw you can import ics files directly into GW ...

GW 18.4.2 backend see this on GW client 18.4.0 and 18.4.1 and 18.4.2. When you try to add the event to the calendar it goes into import and just makes a sub calendar under the main calendar.

Hmm, have you tried to select an existing calendar?

Here is a link to video I made of the problem. https://youtu.be/hVVkG_4r3gM

Nice video. I tried a similar activity and failed too!

It was our mail scanner, we add a banner to inbound mail and it was adding it to the ICS witch would brake the ICS. Our mail scanner vender had to do a patch to fix it.