fatal error in 3.8.11 > 5.4.0 upgrade - need help

[excentryk]

I have fata error message in upgrading process:

500a1 Step #132

Fatal Error Occurred
Error Could not find phrase 'invalid_contenttype_class_specified'. Arguments given were: "0' on /home/dentysta/domains/dentystaxx/public_html/forum/core/vb/types.php : 591

Script: 500a1
Step: 132

Please tell me how can I finish upgrade of my forum?

Now I need to back to 3.8.11 because I need a fix for this step.

Regards.

[Mark.B]

Make sure there are no old vB3 files in the folder. To upgrade to vB5 you must remove ALL old vB3 files first so the forum folder is empty (excluding attachments, avatars etc if they are stored in the file system).

[ABDUR7MAAN]

If you do not find this solution, there is only a full backup of the site
Then follow the steps in the upgrade process

The best and safest way to upgrade to the latest version is following the following steps:
1. Copy the database to work on it independently. And upload it on your site and create a separate folder is your workshop in the upgrade and leave your main forum as if you want to retreat can be referred back to another without problems
2-Upload the fourth version files in your workshop folder and then upgrade to the version 4.
3- After completing the upgrade to the version 4 , we delete the files of the version 4 and put up the files version 5 and then upgrade from the version 4 to the version 5

[excentryk]

Make sure there are no old vB3 files in the folder. To upgrade to vB5 you must remove ALL old vB3 files first so the forum folder is empty (excluding attachments, avatars etc if they are stored in the file system).

of course I've deleted all old files

the problem exist in upgrading process in 500a1 Step #132