Can't open PDFs (and other files) from WhatsApp

I'm using a Xiaomi MI 9 SE phone (Android v11, MIUI Global v12.5.1). For quite a long time now, I've had the problem of not being able to open PDF files attached to WhatsApp messages I receive. When I double-click them, the app I choose either shows nothing, or immediately quits (depends on the app). I tried to check the app permissions, and there are no permissions - that I know off - that WhatsApp is missing. I also tried updating WhatsApp, which didn't help. I do not have this problem with other messaging applications, e.g. Telegram. Also, the different viewers / handling apps are able to open PDFs from other sources. What's the cause of this problem, and what can I do about it? Note: My situation is not the same as in Cannot open PDF files received on WhatsApp directly , where the user was getting an error message about not having the appropriate app for the content type.