I don’t know if it helps, but I’m getting this error on the page that has lots of fields. Similar pages save without this error:
Uncaught TypeError: Cannot read property ‘length’ of undefined jquery.js?ver=1.11.0:2
n.extend.each jquery.js?ver=1.11.0:2
(anonymous function) input.js?ver=5.0.0:5071
_runHook input.js?ver=5.0.0:235
applyFilters input.js?ver=5.0.0:115
$.extend.apply_filters input.js?ver=5.0.0:1098
acf.validation.complete input.js?ver=5.0.0:5231
$.ajax.success input.js?ver=5.0.0:5221
j jquery.js?ver=1.11.0:2
k.fireWith jquery.js?ver=1.11.0:2
x jquery.js?ver=1.11.0:4
b
