It is a known bug in versions prior to 22.214.171.124. It's definitely not correct.
This issue is fixed in version 126.96.36.199. As stated in the release notes:
fixes stale tcp connections
fixes solid milestone getting stuck (regression)
enables checking balance based on tips
enables API Rate limit for ...
This is the basic answer for IRI synchronization issues:
Make sure that your neighbor nodes are active and fully synchronized. If that's the case proceed with step two.
Restart the node once with the parameter --revalidate. It will re validate your database without removing transactions and hopefully fix the issue.