Haven't seen that before ... in every other instance we've seen, map problems have been fixed by the forced refresh. But yes, even if you were having refresh problems, the players would be able to see the updated map (they might have to refresh too, of course to clear their own caches).
H'mmm ... you're not trying to upload an image that's too large, are you ? That would fail and therefore not replace the existing image ... but in that case you'd be getting an informative message telling you it was too big.
Otherwise ... back to basics. What browers are you using ? And what's it's setting for reloading pages, images etc ?
In Internet Explorer 11 (and same/similar in earlier versions, but I don't know about Edge) if you look under Tools | Options ... General Tab, Browsing History section, Settings button it has four options under Temporary Internet Files tab:
Internet Explorer stores copies of webpages, images and media for faster viewing later.
Check for newer versions of stored pages:
o Every time I visit the webpage
o Every time I start Internet Explorer
o Automatically
o Never
Other browsers should have something similar