background only in the first letter of custom fields in writer

users
#1

Hi, I have this file here:
https://mega.nz/file/C9YB2QaI#gpSZBPYE1XzQj4OWRMpEk-xHFHwU1M5d4Bi8Yjr8iuo

I made this file in windows 7, in this file where I have some custom fields (set in File>Properties>custom properties tab) and I tried to set the background (the color was something like bluegray),
in some cases like

Procedura Avvio AAA

it fully succeed, but in other cases like

2021nov16

and

1.2

where the background result only for the first letter (in window 7 the first letter "2" and "1" result corrected backgrounded the rest "021nov16" and ".2" result with no background,
in linux and windows 10 the rest result greyed backgrounded)

Why this and how can I have a corrected backgrounded custom field?