Since you're having this issue only on one specific model of camera, I don't think it will be related to the hotfix rollup previously mentioned. Though, if you're not running version 2016 R3 SP1 (10.2b), it is definitely important to apply that hotfix.
I could be wrong, but it sounds like perhaps there was a change in behavior in the way the Recording Server delivers recorded video and perhaps an underlying issue with the video stream from these cameras is surfacing as a result.
I have seen this type of behavior for example when a camera is sending "jittery" time stamps with the video stream; oddly variable time deltas, two consecutive identical time stamps, or even a time stamp older than the previously received time stamp. Live is generally unaffected because we try to push the image out to clients as soon as we receive it. But playback will be more sensitive to this behavior.
I'm not saying it's a problem with the camera, only that it would be the first thing we should investigate based on the symptoms provided (live is fine, exports are fine, playback for other cameras is fine, only playback for these cameras are affected).
If you haven't already opened a case with us on this, please feel free to copy my hypothesis and attach it to your case. Some things we'll want to collect to help us diagnose the issue may include...
- Milestone Diagnostics Tool and Milestone Analyzer results from the Recording Server
- Wireshark trace between Recording Server and one of the affected cameras for maybe 15 seconds
- A zipped copy of an XProtect format export of an affected camera (maybe 5 minutes tops)
- If possible, a copy of an actual archive table from an affected camera. This is ideal as we can then have R&D investigate the block files frame by frame and determine whether there are "invalid" time stamps that could be causing this behavior. These folders can tend to get pretty big though, so see if you can work with our support team to get a folder zipped up and sent over for analysis. Alternatively depending on your availability/accessibility we can arrange for R&D to review the system remotely
Some things you probably know we're going to ask include...
- Are you using the most recent Device Pack version?
- Is the firmware for the affected cameras the most recent tested firmware version?
- If a newer firmware version than we have tested is available, it may be beneficial to see if there is an improvement when upgrading to the most recent firmware version, even if it has not yet been tested by Milestone (Axis cameras usually roll back firmware gracefully when needed).
Looking forward to seeing what the ultimate cause was. I don't expect you'll have any issues but feel free to reach out to me at jh@milestonesys.com if you have any difficulties.