It’s just a PHP notice, but they are lot of call on this fonction.
I see in my debug.log this error, :
[16-Aug-2018 08:43:32 UTC] PHP Notice: Undefined index: readonly in C:\wamp64\www\retail-portal-wordpress\wp-content\plugins\acf-qtranslate\src\acf_5\fields\text.php on line 100
You can Fix this stack trace with this code:
File: text.php & textarea.php
line: 89 to 104
Just add if with array_key_value