Yes this is an ongoing issue that has been with me since day one, with blame being pushed toward Apple's Mojave requirement of observe only. But I have set all my machines to allow control (manually) and still I get the issue where I can see the remote computer via in browser, or screen sharing hand-off, but I can not move the mouse nor interact in any fashion.
I can do both via local screen sharing or ARD so my guess is the issue lies with Meraki.
I have tried older OS set-ups as well and issue persists. Kinda makes the advertised feature a little bit of a sad trombone. I've been waiting 4 months for a resolution, and the latest theory is that it's a Mojave bug.
One day I'll be able to reach out to my field folks; this is what I keep telling myself, because surely an advertised feature would work, right?