Premiere Pro 26 regression: continuous dropped frames with Canon R5 C XF-AVC Intra MXF files over SMB / 10GbE NAS — works perfectly in 25.6.6

Issue description

Since upgrading to Premiere Pro 26, I am experiencing severe playback issues with Canon EOS R5 C XF-AVC Intra MXF footage stored on a Synology NAS connected through a 10 Gigabit Ethernet network.

Playback continuously drops frames, particularly after moving the playhead to a different position and starting playback. Reducing playback resolution to 1/4 does not resolve the issue.

The exact same files play perfectly when stored on either of my local NVMe SSDs.

Most importantly, Premiere Pro 25.6.6 plays the same MXF files directly from the same NAS perfectly, on the same computer and with the same Windows installation.

System configuration

• OS: Windows 11 Pro 26H2, build 26300.9711

• CPU: Intel Core i9

• GPU: NVIDIA GeForce RTX 4060 series

• NAS: Synology DS1823xs+, 5 HDDs in RAID 5

• Network: 10 Gigabit Ethernet, SMB 3.1.1

• Network adapters tested: Marvell 10GbE and ASUS XG-C100C

• Footage: Canon EOS R5 C, XF-AVC Intra, MXF, 59.94 fps

• Working version: Premiere Pro 25.6.6

• Affected version: Premiere Pro 26.x (latest installed version; exact build to be supplied)

Steps to reproduce

1. Create a completely new Premiere Pro 26 project on a local NVMe SSD.

2. Import a Canon R5 C XF-AVC Intra MXF file stored on the NAS via SMB.

3. Open the clip in the Source Monitor.

4. Enable the dropped-frame indicator.

5. Move the playhead to different positions and start playback.

6. Observe continuous dropped frames, even at 1/4 playback resolution.

7. Copy the same MXF file to a local SSD and repeat the test: playback is perfectly smooth.

8. Open Premiere Pro 25.6.6, create a new project, and import the original MXF directly from the same NAS: playback is perfectly smooth.

Additional troubleshooting already performed

• Verified NAS sequential read performance: approximately 900–950 MB/s.

• Confirmed SMB 3.1.1 connectivity.

• Tested two different 10GbE network adapters with identical results.

• Moved the Premiere project, media cache and preview files to a local SSD.

• Reset Premiere Pro 26 application preferences.

• Deleted and regenerated media cache.

• Updated Premiere Pro 26 to the latest available version.

• Confirmed that both local NVMe drives play the footage correctly.

• Tested completely new projects in both Premiere versions.

None of these actions resolved playback in Premiere Pro 26.

Expected result

Premiere Pro 26 should play the same Canon XF-AVC Intra MXF files directly from the NAS without dropping frames, as Premiere Pro 25.6.6 does on the identical system.

Actual result

Premiere Pro 26 continuously drops frames during playback from the NAS. The same media plays smoothly from local SSDs and also plays smoothly over SMB in Premiere Pro 25.6.6.

Conclusion / Request

This strongly suggests a regression in Premiere Pro 26 related to MXF media playback over SMB network storage.

Please investigate the differences in network media reading, caching, buffering or MXF handling between versions 25.6.6 and 26.x.

This issue significantly affects professional editing workflows using shared NAS storage.