Http error 500 for new registrations after upgrade to 1.8.20

[ArchPrime]

My site seems to be working well apart from new signups, who are getting 'HTTP error 500' whenever submitting their correctly completed user registration form.

To address suggestions I found for similar error 500 issues reported by users after previous version upgrades:

This was not an issue for me under the previous version 1.8.19

I performed the recommended upgrade procedure from 1.8.19 to 1.8.20

My server's error logging is enabled in public_html/php.ini
My server error log is however completely empty
My server is running php version 7.2.13
Tapatalk plugin has been deactivated in MyBB
MyBB ACP 'File verification' reveals' all files are ok
All files have correct CHMOD permissions
'Check Templates' reveals all ok

What is likely wrong?
Is this a known bug?
How can I sign up new users?

Any help most appreciated!

[WallBB]

Weird thing is all your templates are okay. What I feel is that this is mostly related to the theme because MyBB 1.8.19 and 1.8.20 have theme related changes as well.
Can you verify all your updated templates related to login in 1.8.20 with your theme's template ?
All templates are here
https://mybb.com/versions/1.8.20/

[ArchPrime]

Weird thing is all your templates are okay. What I feel is that this is mostly related to the theme because MyBB 1.8.19 and 1.8.20 have theme related changes as well.
Can you verify all your updated templates related to login in 1.8.20 with your theme's template ?
All templates are here
https://mybb.com/versions/1.8.20/

Thanks WallBB

As a test, I switched the default theme to a copy of MyBB Master Style, and tried again to register as a new user

Under Chrome browser, instead of error 500 I  now got 'Error - invalid time type'.  Under Edge browser I get no error, but just a blank page.
The time zone settings submitted were correct, and the default time zone settings autodetected by Chrome (presumably).

Is this informative?  Is this 'time type' a bad user setting, or a scripting error? 

I looked through the changed files download in https://mybb.com/versions/1.8.20/ but could not find any on the server that had not been replaced with these already.  However, I re-uploaded them all anyway, overwriting the existing on server - with no improvement

[WallBB]

Weird thing is all your templates are okay. What I feel is that this is mostly related to the theme because MyBB 1.8.19 and 1.8.20 have theme related changes as well.
Can you verify all your updated templates related to login in 1.8.20 with your theme's template ?
All templates are here
https://mybb.com/versions/1.8.20/

Thanks WallBB

As a test, I switched the default theme to a copy of MyBB Master Style, and tried again to register as a new user

Under Chrome browser, instead of error 500 I  now got 'Error - invalid time type'.  Under Edge browser I get no error, but just a blank page.
The time zone settings submitted were correct, and the default time zone settings autodetected by Chrome (presumably).

Is this informative?  Is this 'time type' a bad user setting, or a scripting error? 

I looked through the changed files download in https://mybb.com/versions/1.8.20/ but could not find any on the server that had not been replaced with these already.  However, I re-uploaded them all anyway, overwriting the existing on server - with no improvement

Very weird, can you check the console log on the registration page since the error is on that page only ?

[ArchPrime]

Weird thing is all your templates are okay. What I feel is that this is mostly related to the theme because MyBB 1.8.19 and 1.8.20 have theme related changes as well.
Can you verify all your updated templates related to login in 1.8.20 with your theme's template ?
All templates are here
https://mybb.com/versions/1.8.20/

Thanks WallBB

As a test, I switched the default theme to a copy of MyBB Master Style, and tried again to register as a new user

Under Chrome browser, instead of error 500 I  now got 'Error - invalid time type'.  Under Edge browser I get no error, but just a blank page.
The time zone settings submitted were correct, and the default time zone settings autodetected by Chrome (presumably).

Is this informative?  Is this 'time type' a bad user setting, or a scripting error? 

I looked through the changed files download in https://mybb.com/versions/1.8.20/ but could not find any on the server that had not been replaced with these already.  However, I re-uploaded them all anyway, overwriting the existing on server - with no improvement

Very weird, can you check the console log on the registration page since the error is on that page only ?

Hi, I am not sure how best to get a console log, but the attached is what I see in Chrome console as soon as the error 500 occurs