Problem with Facebook and iPhone: typing is slow, even after completely resetting the iPhone and without restoring from iCloud.

Hi guys, let me explain a problem my girlfriend is having with VoiceOver, the iPhone, and the Facebook app. When she writes a comment, she experiences a slowdown while typing and when using VoiceOver to read the characters she has typed. We had the same iPhone model, the SE 2022, and I didn’t have this issue. Now she got the iPhone 16, and the problem still persisted!
Since she still had the older phone available, I had her completely reset the iPhone and set it up as new, without restoring from iCloud — the problem disappeared! So, I had her do the same on the iPhone 16: reset and don’t restore from iCloud. The problem went away for a few hours, but after installing WhatsApp, YouTube, Google, Instagram, and other apps, the slowdown came back.
Now I don’t know if it’s caused by one of those apps or something else. Do you have any suggestions?
Thanks,
Ambro