Upgrade Error

Hi,
I am a complete novice when it comes to Opencart. I am helping a friend set up online presence so I have set up a completely test store to see how the process goes.
So far we have been managing OK but now I tried updating from 3.0.3.8 to 3.0.3.9 and I did it via Softaculus.
But when applying the upgrade I got the following error. As you might have guessed I am clueless on what to look and what to do to fix this.
Extensions I have installed are from Cardlink a credit card company, Mega Filter, Greek Store Translation, Autofill Meta tag and a Greek map.
Everything else is stock. As I said this is a completely test platform. Any help is greatly appreciated.

SyntaxError: JSON Parse error: Unrecognized token '<' OK Warning: mysqli::query(): (42S22/1054): Unknown column 'pt.tag' in 'field list' in /home/xhmeia/public_html/system/library/db/mysqli.php on line 25{"error":"Error Code(0): Error: Unknown column 'pt.tag' in 'field list'
Error No: 1054
SELECT p.product_id, GROUP_CONCAT(DISTINCT pt.tag order by pt.tag ASC SEPARATOR ',') as tags FROM oclm_product p LEFT JOIN oclm_product_tag pt ON (p.product_id = pt.product_id) WHERE pt.language_id = '1' GROUP BY p.product_id in \/home\/xhmeia\/public_html\/system\/library\/db\/mysqli.php on line 49"}

The "product_tag" database table hasn't existed since early OpenCart 1.5 versions, so you're probably using a mod that isn't coded for 3.0 (or it's doing a check wrong and thinks your installation is an old OpenCart version). You will need to try disabling/removing the extensions you've installed one-by-one until you can figure out which one it is. I'm guessing Mega Filter or the Autofill Meta Tag extensions.

You might also double-check that the VERSION constant is set right in your index.php and admin/index.php files. Sometimes language packs change that constant and that can mess up extensions. You always want to leave it as your actual OpenCart version, so it should look like this in your case:

define('VERSION', '3.0.3.9');

Thank you for the pointers on what to look out. I try the suggestions and then comeback with an update.