Well, this could be happening for any number of reasons. It could be a problem with your link, it could be high usage of the box, it could be an application problem.
Do you have link balancing active? If so, have you tried to create an SD-WAN rule forcing this traffic to this specific destination and giving preference to only one of its links?
Something like this.
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.