Yep, I've been experiencing a lot of issues with this version like, performance, S2S VPN,etc. You are not the first case that related this issue with the same version, and all was solved after downgrade It. You asked for a suggestion and my suggestion is try downgrade It, but It's your choice.
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.