We have been recently experiencing a very large number of conflict messages on Shifts. It appears this issue emerged after the latest update.
The most common conflict we are getting is a message that says "Person's name isn't available on date".
I have looked high and low to try and find if Teams allows you to set your own availability and have found nothing. This issue is particularly problematic when time off requests are made as it creates a conflict for every day. I have over 50 folks on my schedule...
In the Teams mobile app under the Shifts app, tap the "+" in the upper right-hand corner. Then, select "Set Availability" and set as desired. This setting appears to only be configurable by the end user, so you'll need to tell the person with the conflict to go in and make this change.