The form keeps showing the same mistake

Hello,

They have created a test script to check sening messages from the website
http://stegantsov.com/test_sendmail.php the messages are sent successfully.

It’s php 5.4,

they turned on debug mode, installed capcha but the problem still exists in logs it gives this info:

[Fri Jul 15 21:26:21.830873 2016] [:error] [pid 16090] [client 81.95.20.130:41808] PHP Notice: \xd0\x92\xd1\x8b\xd0\xb7\xd0\xb2\xd0\xb0\xd0\xbd\xd0\xbd\xd1\x8b\xd0\xb9 \xd0\xbc\xd0\xb5\xd1\x82\xd0\xbe\xd0\xb4 \xd0\xba\xd0\xbe\xd0\xbd\xd1\x81\xd1\x82\xd1\x80\xd1\x83\xd0\xba\xd1\x82\xd0\xbe\xd1\x80\xd0\xb0 \xd0\xba\xd0\xbb\xd0\xb0\xd1\x81\xd1\x81\xd0\xb0 WP_Widget \xd0\xb2 STTabContent \xd1\x81\xd1\x87\xd0\xb8\xd1\x82\xd0\xb0\xd0\xb5\xd1\x82\xd1\x81\xd1\x8f \xd1\x83\xd1\x81\xd1\x82\xd0\xb0\xd1\x80\xd0\xb5\xd0\xb2\xd1\x88\xd0\xb8\xd0\xbc \xd1\x81 \xd0\xb2\xd0\xb5\xd1\x80\xd1\x81\xd0\xb8\xd0\xb8 4.3.0! \xd0\x98\xd1\x81\xd0\xbf\xd0\xbe\xd0\xbb\xd1\x8c\xd0\xb7\xd1\x83\xd0\xb9\xd1\x82\xd0\xb5
__construct()
. in /home/u18436/data/www/stegantsov.com/wp-includes/functions.php on line 3718, referer: http://stegantsov.com/contact/
[Fri Jul 15 21:26:21.863143 2016] [:error] [pid 16090] [client 81.95.20.130:41808] PHP Notice: Undefined index: path in /home/u18436/data/www/stegantsov.com/wp-content/plugins/stToolKit/inc/functions.php on line 21, referer: http://stegantsov.com/contact/

Can you tell what they should do to fix the problem? We’ve run out of ideas 🙁