You're assuming it's a Meraki problem but you're not sure.
I don't remember if you informed the software version that is running on the MX, but if I were to bet on something, I would say that it is a version problem. I myself have had issues printing over the network and RDP with any 18.x version and had to downgrade.
In your place I would open a support case.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.