Hello Adobe Community,
I'm experiencing an issue with hardware-accelerated decoding in Adobe Premiere Pro on my NVIDIA RTX 5070 Ti GPU. Specifically, HEVC (H.265) videos in 4:2:2 chroma subsampling, 10-bit depth work perfectly with hardware decoding at 4K resolution, but the same format at 6.2K (5240x2700) falls back to software decoding (CPU). This leads to poor performance during playback and editing.

System Specs:

GPU: NVIDIA RTX 5070 Ti (latest Studio Driver installed, 581.57)
CPU: AMD Ryzen 9 9900X
RAM: 64GB DDR5
OS: Windows 11 (fully updated)
Premiere Pro Version: 25.5
Preferences > Media: Hardware-accelerated decoding enabled, set to NVIDIA.

Issue Description:

For 4K videos (4096x2160 or 3840x2160), hardware decoding works as expected. In the Debug Monitor (Alt+Ctrl+F12 > Importer.MPEG), the "Hardware Decompressed" counter increases while playing, and "SW Frames Decompressed" stays at 0. GPU usage is visible in Task Manager/GPU-Z.
For 6.2K videos (5240x2700 from Fujifilm X-S20 camera), it switches to software decoding: "SW Frames Decompressed" increases, but "Hardware Decompressed" remains at 0. No GPU decode activity.

Both videos have very similar properties (HEVC High Profile, Level 6.1, 10-bit, 4:2:2, YUV). The only major differences are resolution and frame rate (6.2K at 25fps, 4K at ~60fps). I've tried:

Clearing media cache.
Restarting Premiere after enabling hardware decoding.
Testing with different sequences and clean projects.
Updating drivers and Premiere to the latest versions.

This seems like a limitation or bug in the Mercury Playback Engine's integration with RTX 50-series NVDEC for higher resolutions in 4:2:2. Encoding works fine for both resolutions.

Has anyone else encountered this with RTX 50-series cards and high-res HEVC 4:2:2? Is this a known limitation, or could it be fixed in a future update? Any workarounds besides proxies or transcoding to ProRes?
Thanks in advance for any help!