hi phil,
sorry for the late reply.
here are 2 examples of those jpegs:
jpeg1
jpeg2
my template-file consists of 2 lines:
Cam: $Model ($ShutterCount) ... Linse: $Lens @ $FocalLength
$ShutterSpeed s ... F $Aperture ... ISO $ISO ... EV: $ExposureCompensation ... Focus: $focusmode

This template worked with older exiftool versions (7.6.x) with those files too.
In newer Versions some (unused) Tags of the template stops the whole decoding.
I think these tags doesnt exist in those "crippled" files (Warning: [minor] Tag 'ShutterCount' not defined - ...)
hmmm, its only a warning, but exiftool aborts the process. I found the -m parameter (for errors)
My solution is the -m parameter, so exiftool doesnt abort when warnings appearing *wondering*
alfterall, my now working command is
exiftool -m -p e.tpl ...
cu, bozi