1.8.6 doesn't show .mp4 files in preview

[Odd]

The latest version of XnView MP (and the previous versions) shows neither a thumbnail nor a preview picture in the browser. I can open and display the file. Here is the MediaInfo report for an example file:

General
Complete name : T:\Bilder'\Camera\VID_20191009_150559.mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42 (isom/mp42)
File size : 249 MiB
Duration : 1 min 43 s
Overall bit rate : 20.2 Mb/s
Frame rate : 29.824 FPS
Encoded date : 2019-10-09 13:07:51 UTC
Tagged date : 2019-10-09 13:07:51 UTC
xyz : +43.2837+003.5222/
com.android.version : 9

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L4
Format settings : 1 Ref Frames
Format settings, CABAC : No
Format settings, Reference frames : 1 frame
Format settings, GOP : M=1, N=30
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 min 43 s
Bit rate : 20.0 Mb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Rotation : 180°
Frame rate mode : Variable
Frame rate : 29.824 FPS
Minimum frame rate : 7.757 FPS
Maximum frame rate : 34.682 FPS
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.323
Stream size : 247 MiB (99%)
Title : VideoHandle
Language : English
Encoded date : 2019-10-09 13:07:51 UTC
Tagged date : 2019-10-09 13:07:51 UTC
Color range : Limited
colour_range_Original : Full
Color primaries : BT.709
colour_primaries_Original : BT.601 NTSC
Transfer characteristics : BT.709
transfer_characteristics_Original : BT.601
Matrix coefficients : BT.709
matrix_coefficients_Original : BT.601
mdhd_Duration : 103642
Codec configuration box : avcC

Audio
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 1 min 43 s
Source duration : 1 min 43 s
Bit rate mode : Constant
Bit rate : 156 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 1.92 MiB (1%)
Source stream size : 1.92 MiB (1%)
Title : SoundHandle
Language : English
Encoded date : 2019-10-09 13:07:51 UTC
Tagged date : 2019-10-09 13:07:51 UTC
mdhd_Duration : 103444

[Odd]

The same applies to .MOV files.
Attached are two samples.

[xnview]

no problem here, 'show as thumbnail' is enabled in Settings>Custom filter for video?

[Odd]

I just discovered that myself. See my comment to my bug report on AVI files and make "Show as thumbnail" the DEFAULT setting!