Think this issue is major if you have a lot of user with email about error.

Currently : there are no error show for user (AddWarning didn't work so good ;) . Only email was sent.
debug 2 or 0 : same things

Checked : only an Equation

The reponse attributes are

    1 => array
    (
        'id' => '5'
        'token' => 'TEST'
        'submitdate' => '1980-01-01 00:00:00'
        'lastpage' => '1'
        'startlanguage' => 'en'
        'seed' => '867823954'
        '958824X1333X24056' => 'aaaa'
        '958824X1333X24061' => '1'
        '958824X1334X24057' => ''
    )

The value to update

    2 => array
    (
        'lastpage' => 1
        '958824X1333X24061' => '1'
    )

Manually adding a broken column : debug set to 2 + debugsql

    (
        'lastpage' => 1
        '958824X1333X24061' => '1'
        'brokenattribute' => 'SQL broken'
    )

No error
SQL done :

system.db.CDbCommand.execute(UPDATE `lime_survey_958824` SET `lastpage`=:yp0, `958824X1333X24061`=:yp1 WHERE `lime_survey_958824`.`id`=5. Bound with :yp0=1, :yp1='1')

https://github.com/LimeSurvey/LimeSurvey/pull/1371

This fix the issue … but … i like to be sure it's due to PDO system :)

Launch TEST token survey

What to do after this?

You didn't receive an email ?
If not : update email adress

PS : for checking : i add a tracevar('bad submit') in expression manager https://github.com/LimeSurvey/LimeSurvey/pull/1371/files#diff-796aba4d06254b9caea9d461e4ea80c9L5585

An error occurred saving a response to survey id Check admin warning - 434875

DATA TO BE ENTERED:
token: TEST
434875X1348X24275: aaaa
434875X1348X24277: 1
434875X1349X24276: 
434875X1348X24275: aaaa
434875X1348X24277: 1
434875X1349X24276: 

SQL CODE THAT FAILED:
Error on response update

Fixed in Release 3.21.6+200121