“Find on Page” only finds word spelled backwards in some PDFs opened in Safari on iPad or iPhone (iOS 17, maybe 16 too)

Searching certain PDFs while viewing them in safari it looks for the text string as it would be reversed. I noticed it as I searched a page number 112 and it returned 211 - so I did some trial and error. When I searched for “illness” (a word used many times in the document) I got nothing. When I searched for “ssenlli” it found all occurrences of the word “illness”. It’s the same for anything I search - I have to type the string in reverse. If I search words on the title page of this particular documnt it finds them as expected and other entire PDFs work as normal. But several (perhaps all) of the publications from this particular site seem to have the “backwards string” search issue. I hadn’t noticed before today but don’t use this feature for PDFs in safari a lot as I usually download them.

I may have had the problem previously (It tends to manifest as not finding what I searched even though the word was obviously there - until you realize the backwards string issue) and just moved on and ignored it and forgot about it (I have a vague memory of experiencing this). Today it stood out as I just upgraded to iPadOS17.1.1 yesterday and am primed to blame any bug on the new OS. I found another thread in this discussion forum where many people (over 800) reported problems with search on page not finding words that were clearly in a PDF and they felt it started with iOS 16, I’m wondering if that might have been the case for me but I didn’t take notice or follow up on it. In fact I only updated to 16 relatively recently on my iPad (where I use the feature more as I have a keyboard). The same problem occurs on my phone (iPhone 12 mini just upgraded to 17.1.1, but was updated to 16 relatively early after release) so the vague memory may have been from being confounded on my iPhone but letting it go and moving on without investigating the forums.

my iPad is 3rd gen (2018) 12.9” pro

I’ve included 2 screenshots of the issue in action below. First with it finding a word when I spell it backwards, Second with it not finding any instances of the same word spelled properly: