Search bar in Messages doesn't work after transferring to a new phone

I just transferred all my data from an iPhone X (256 gb, 15.2) to an iPhone 13 Pro (512 gb, 15.2) and I haven't been able to use the search bar in Messages properly.

On my old phone, I was able to type in a certain phrase and it could pull up every time the phrase was mentioned between now and 2014 (when I got my phone). However, after the transfer, I was unable to search through any older messages older than a few days.

I did some googling and turned the search settings with Siri on and off, then restarted the phone etc. I was able to get the search function back online, but unfortunately the search index appears to skip all of June 10, 2021, to December 26, 2021. I can search for messages before and after this window, but nothing in between.

Other related issues: I was unable to view chat attachments in the conversation details window, despite the attachments existing if I scrolled back far enough.

What gives?