If you cut your finger with a knige you say "the knife have a bug", or better "I do not know how properly use a knife"?
paste this on terminal and share the result:
/file print where name~"json"
nevermind the RouterOS version.
If a file called
skins/default.json
or
flash/skins/default.json
or simialr is present,
just delete that file:
/file remove "skins/default.json"
From 7.x.x version, (I do not remember exactly from what version) skin is applied not only on webfig but also on winbox
If someone (you) has played before with webfig skin, now winbox apply the results, until you do not delete the file or re-edit the skin on webfig....