Grey screen

[mt_subnet]

Avidemux 2.6.20 Debian 9.11 Humax FVP-5000T
I Move recordings via usb HDD to my laptop and edit out adverts all is fine except one recording which I can play on SMplayer or Avidemux but when I switch to frame by frame or minute by minute there is no picture just a grey frame. Any ideas?

[eumagga0x2a]

Avidemux 2.6.20

...which is an unsupported legacy version. Does the latest appImage (currently from 2020-01-23) fail to run on Stretch?

https://avidemux.org/nightly/appImage4/

Alternatively, please consider building Avidemux from git master source yourself.