14.0.3 update

Does it happen with all mkv and m4v files or just some of them? You can use Explorer > Right-click > MediaInfo to see details.

A link to any of the problematic files would be useful. Then I can test with same file.

far as i know, it happens to all my m4v files (i have 4). i dont know about mkv because i only have 1 file. last time i checked, all download links are dead.

all my m4v files have similar details

General
Complete name : D:\Idol\hd_akbingo_ep402.m4v
Format : MPEG-4
Codec ID : M4V (isom/iso2/avc1)
File size : 1.74 GiB
Duration : 1 h 0 min
Overall bit rate mode : Variable
Overall bit rate : 4 144 kb/s
Writing application : Lavf57.56.101

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 h 0 min
Bit rate : 4 000 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 (29970/1000) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.145
Stream size : 1.68 GiB (97%)
Writing library : x264 core 148 r2643 5c65704
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=abr / mbtree=1 / bitrate=4000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Menus : 3

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : mp4a-40-2
Duration : 1 h 0 min
Bit rate mode : Variable
Bit rate : 128 kb/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 54.8 MiB (3%)
Language : Japanese
Default : Yes
Alternate group : 1
Menus : 3

Menu #1
ID : 3
Codec ID : text
Duration : 1 h 0 min
Language : English
Menu For : 1,2
00:00:00.000 : Chapter 1
00:01:24.851 : Chapter 2
00:10:00.700 : Chapter 3
00:17:00.953 : Chapter 4
00:25:15.781 : Chapter 5
00:32:37.556 : Chapter 6
00:38:57.602 : Chapter 7
00:45:49.347 : Chapter 8
00:52:47.931 : Chapter 10
Bit rate mode : VBR

Menu #2
00:00:00.000 : Chapter 1
00:01:24.851 : Chapter 2
00:10:00.700 : Chapter 3
00:17:00.953 : Chapter 4
00:25:15.781 : Chapter 5
00:32:37.556 : Chapter 6
00:38:57.602 : Chapter 7
00:45:49.347 : Chapter 8
00:52:47.931 : Chapter 10

do you think it has something to do with the newest mpc hc changelog?

Changelog 1.7.15 to 1.7.16:

* Updated LAV Filters to v0.71-25
* Updated MediaInfo DLL to v18.03.1

! Limit inaccuracy of fast seek to 20 seconds. This also fixes seeking in files that have invalid keyframe timestamps.

i thought so lol

No, that should be unrelated, unless your files have huge keyframe intervals. Vamong already tested with older MPC-HC.

Perhaps you could upload a sample file?

If it is too big then you can can cut a 20MB (or more) sample with this little tool:
http://rationalqm.us/dgsplit/dgsplit12.zip

Then upload to http://www.sendspace.com or a similar site.