Can't search older posts

I needed to check an old post in the forum. Sadly I could not remember
the title, and generic word-search was fruitless.

Since it wasn't a thread I started, but an answer I made to another
person, I could not look for the "Find all threads started by me".

So I decided to check my old posts. When looking at the "Find all posts
by ···(me)" in my profile, it shows only the more recent 500 posts I made
(out of the more than 2000 I've written), and can't go back any further.
The thread was more than 3 years old, so obviously doesn't show
in the results (my most recent 500 messages are from this year alone).

I tried to do the same in another person's profile, and again it only shows
the 500 more recent posts, not all of them.

Last time I used this function was a couple of months ago and it was
working fine, could reach my very first posts in the forum. But today I
found it is faulty.

The suggestion to the administrators is to check that ;)

Thank you!