Package updater partially uses secondary language instead of primary one

Describe the bug
Language for the interface is set to en-gb.
Nl-nl is used for region and time format.

While generally en-gb is indeed used for menus etc., the status window for the package window mixes the two languages.

Not sure since when the issue started appearing. Might be the major update from last (?) week or me changing the primary language from en-us to en-gb last week or the week before.

Screenshots
Sorry, screenshot tool and I are having issues today... screenshot is lost.

Basically, the window title is in English, the title above the progress bar as well.
But the currently performed action is in Dutch, e.g. " configureren" instead of "Configuring .

To Reproduce
I guess:

Bit tricky to reproduce since an update needs to be available in the repos

Distribution:
LMDE Gigi

Software version:
7.1.4

Logs:
The ones related to the screenshot above are not available anymore.

Additional context
Add any other context about the problem you think might be relevant.

Locale:
LANG=en_GB.UTF-8
LANGUAGE=en_GB
LC_CTYPE=nl_NL.UTF-8
LC_NUMERIC=nl_NL.UTF-8
LC_TIME=nl_NL.UTF-8
LC_COLLATE=nl_NL.UTF-8
LC_MONETARY=nl_NL.UTF-8
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER=nl_NL.UTF-8
LC_NAME=nl_NL.UTF-8
LC_ADDRESS=nl_NL.UTF-8
LC_TELEPHONE=nl_NL.UTF-8
LC_MEASUREMENT=nl_NL.UTF-8
LC_IDENTIFICATION=nl_NL.UTF-8
LC_ALL=

No file, test, or entry point is named. Start by reproducing an available package update with LANG=en_GB.UTF-8, LANGUAGE=en_GB, and the listed nl_NL regional settings; trace where the package action text gets its locale. Done means the update window consistently uses en-GB for interface and action text while retaining nl-NL regional formatting.