difficultchild

version 5.4.1 works for me.
i think, because i tested a lot, the problem was a “content/script blocker”.
for me “borlabs cookies”. the shortcode from borlabs worked until version 5.3.2, but not anymore from version 5.4.
I removed the blocker and everything works with the new cf7.

i also did the rollback (the only solution) but i don’t have the problem with the ajax-loader.gif.
maybe because my forms are created with cf7 skins.
i have a normal success-message under the form, that’s enough for me.

much more important is a solution to the problem, otherwise we will still have version 5.3.2 in 4 years.

i still have the problem too. only a rollback to 5.3.2 helped me.
which cache plugin are you using?
maybe it would make sense to exclude the page with the form from the cache plugin.
but that’s not an actual solution, that’s just dirty.