Forum acting weird: not showing up posts/wrong order

[Xarwin]

Hello everyone,

I've been using vbulletin for a while now and I never encountered a problem until now.
I am not sure if it has to do with some plugins. I don't believe it is a plugin and that is why I am asking for help.

Since short members (including myself) are unable to see new posts in a specific forum.
It can be seen in the "new recent threads" block from vBadvanced CMPS and also in the forum index as a link.
Clicking on that link works. Going back to that forum makes you unable to see it.
--> I found out that the topic can be found somewhere on page 3 (for some weird reason?!).

Posting in other forums works and posts are visible. However, they are placed in a strange location for no reason (not at top as newest but as second last).

Whenever checking the forums I am unable to find the problem.
I am using the current settings for all forums:

[Default View Age: show all threads
Default Sort Field: thread title
Default Sort Order: ascending
Show Private Forum: use default

I've ran all maintenance tasks.
And these are my plugins:

vBulletin 3.8.7
BF-Spammer User / Bot Stopper
Cyb - Advanced Forum Rules (disabled)
Cyb - PayPal Donate 4.8.2
DragonByte Tech: Advanced Post Thanks / Like (disabled)
Easy Forms 3.7
Farcaster's Event Attendance
Logician's WebTemplates
Lower Breadcrumbs
Members who have Visited
vB Tournaments and Ladders
vBadvanced CMPS 3.2.2
vBCode table
vBShout 2.0
Yet Another Award System

Any help or suggestions are really appreciated.
Also, thanks in advance for checking out this thread.

[Lynne]

If you have your Default Sort Field set to be Thread Title, then that means you want the threads arrange alphabetically by thread title, not by Last Post Date (which would be newest first).

[Xarwin]

How could I've overseen that!
Thank you Lynne!

I still don't get how it automatically changed like that..