when using JEM2 and php7 you might be seeing some issues in the error logs. I'm sure the dev (Hoffi1) and the rest of the team will be looking into it but if you do see some issues i would recommend to post it here.. You may also post it at Github but you know a member of the team can also post the issue to Github if it's needed.
Due to a recent support question here in the forum i did test JEM 2.2.3 and php 7.3.x locally and did ran into several issues, so yep i do know there are some around. One of them will be icalcreator. Am not posting the issues here as i do like to see where you are running into.