Do you use the mobile or web app? If not, can you please navigate to Quicken > Preferences > Mobile, Web & Alerts, and see if the sync is on.
If you do not actively use the mobile or web app and do discover that is sync is enabled, I would try disabling the sync and see if the behavior improves.
If this is not the issue, I would next recommend contacting support directly for advanced troubleshooting steps.
https://www.quicken.com/support#contact-support
Quicken Care has the tools to review the log files to help determine what is happening to these transactions.
Thank you,
-Quicken Tyka