activity animated icon in print panel stop animating after first print, only in Firefox

[ochriste]

in the print panel, when starting a print job, there is a small animated icon displayed beside the text "votre impression est en cour".

this animated gif is not animating when doing a second or more print job.
only visible in Firefox.
maybe related to https://bugzilla.mozilla.org/show_bug.cgi?id=129986 ?