Pleco document reader - weird highlights on iPhone

So I recently transitioned from Android to iPhone. One of the worst decisions of my life, though that might just be unwillingness (to set aside time for learning) to change old ways of doing things on my side.

In any case, the Pleco migration was pretty smooth and despite some minor differences (there might be bigger ones I haven't discovered yet) from Android the overall experience of using the app is very familiar. I also am most grateful for the fact that for the one-time fee I paid more than a decade ago, I am still able to use this app in both the Android and Apple ecosystem. The fact that Pleco hasn't gone subscription based yet is pretty outstanding.

Anyways. One quirk I am struggling to get to the bottom of. Years ago I bought "The Journey to the West" ebook from Imagin8 Press. I never finished it, and thought I'd load it into the Pleco reader to continue from where I left off. It's an epub file.

The below screenshot shows how the pages look on my desktop reader:

Here's how it looks on Android (Night mode):

Here's how it looks on my iPhone (Night mode):

Now, the yellow text part is a choice I've made in the settings. But the white highlight is have no idea where is coming from. I see no way to control it, or the font color of the text it contains. When I'm reading in the evening I will reduce the brightness and active the "Reduce white point" setting as it feels better on my eyes, and that makes the white highlight part impossible to read. I first thought it only applied to the pinyin paragraphs (and that it was something the author had added, which it may still be? though I have no idea why it appears only on iPhone) but as seen in the screenshot, it covers part of the hanzi paragraphs as well.

Here are my "Document Settings":

I've tried playing around with the colors but cannot see any way to remove the highlight. I've also tripple-checked that it's the exact same file I have loaded to Android/iPhone/Desktop.

Any idea what might be going on?

This is an EPUB, right? It seems like it must have some background color setting that our EPUB reader isn't catching and overriding - on Android we preserve a lot less formatting in EPUBs (we send it through a Google system that converts them into basic rich text) while on iOS we preserve more of it so it's not an uncommon thing to see differ between them.

Anyway, in general the easiest fix for EPUB formatting issues is to open up your EPUB in Calibre (https://calibre-ebook.com) and export it from that to TXT, which should be nice and clean and lack any extraneous formatting.

Thank Mike. It is indeed an EPUB. Converting it to .txt worked like a charm!