Latest MPC-HC, some 720p videos stutter despite good GPU and CPU

[creedo]

Sorry if this isn't the right place to ask. I've been googling for a while and just can't find a solution that works for me.

MPC-HC is playing my 1080p videos flawlessly, yet I have a handful of 720p MKVs that are very choppy. They appear to be H.264 video, AAC audio. Actually just the video is choppy, audio is fine.

These same MKV's play back fine in VLC, so I'm sure this is just a setting thing. The hardware is a Core i5-4460 and an R9 300 video card. Running win7 pro 64.

I'm wondering if it has something to do with the program failing to take advantage of my GPU?
Here are the fixes I've tried so far.

• Uninstalled all codec packs, ffdshow, etc. I actually just reformatted so I've only installed MPC-HC, VLC, and the latest video card driver.

• Options -> playback -> output -> tried Enhanced Video Renderer (custom presenter) and also System Default.

• Options -> internal filters -> video decoder -> hardware decoder -> tried DXVA2 (native), NVIDIA CUVID, and none.

• No custom shaders have been added or enabled.

Any ideas? Again VLC plays these files fine, but I would like to just use mpc-hc for everything.

Here's the codec info if it helps:

Video
ID                             : 1
Format                         : AVC
Format/Info                    : Advanced Video Codec
Codec ID                       : V_MPEG4/ISO/AVC
Duration                       : 47mn 35s
Bit rate                       : 2 084 Kbps
Width                          : 1 280 pixels
Height                         : 720 pixels
Display aspect ratio           : 16:9
Frame rate mode                : Constant
Frame rate                     : 23.976 fps
Bits/(Pixel*Frame)             : 0.094
Stream size                    : 709 MiB (83%)
Default                        : Yes
Forced                         : No

Audio
ID                             : 2
Format                         : AC-3
Format/Info                    : Audio Coding 3
Mode extension                 : CM (complete main)
Format settings, Endianness    : Big
Codec ID                       : A_AC3
Duration                       : 47mn 35s
Bit rate mode                  : Constant
Bit rate                       : 384 Kbps
Channel(s)                     : 6 channels
Channel positions              : Front: L C R, Side: L R, LFE
Sampling rate                  : 48.0 KHz
Compression mode               : Lossy
Stream size                    : 131 MiB (15%)
Default                        : Yes
Forced                         : No