Upgraded our MX68 estates to 15.43 yesterday all sites reported network issues. Rolled the upgrade back and stability was restored. Unforunately, I was not informed until after the downgrade took place.
We have 12 remote networks configured for AutoVPN with a central MX400 which was also upgraded to 15.43. The the dashboard indicated a problem the autovpn feature having stability issues. VPN's were constantly going down. Stopped once we rolled back to 14.53
If you haven't already, I'd ask to raise a case with the Support Team. If 15.43 is causing this type of problems, we surely want to gather enough data to create a report for the developers so that it doesn't impact subsequent releases.
For VPNs in particular it's always good to grab packet captures on the Internet interfaces of the MX(s) and attach them to the cases along with timestamps so we can check logs in the backend.
Would also be interesting to see if the issues are with MXs that are directly public facing or behind NAT.
Please keep in mind that what I post here is my personal knowledge and opinion. Don't take anything I say for the Holy Grail, but try and see! Appreciate who helps and be respectful of every opinion and every solution offered. Share the love, especially the Meraki one!