iPhone clipboard forgets contents after 20 minutes or so?

Clearly I'm not the only one having this problem:

https://discussions.apple.com/thread/250114802?answerId=250218420022#250218420022

That thread appears to be locked. I did some basic ad-hoc testing and the clipboard works fine, copying and pasting in "notes", until I let my phone sit for 20 minutes or so (didn't get an exact time), after which "paste" pastes nothing. I don't know if the clock starts ticking from when I last pasted, or from when the original copy occurred. The problem appears in many different apps, so it's not app-specific.

This was not always the case. I do property management, and when showing apartments to multiple people in the same day, I want to text interested people a link to our application form. Previously, I just copied the link in the clipboard, and it would stay there all day as long as I didn't copy something else. I could just paste the link into each person's text. But then, after a certain iOS update (probably iOS 12?) this ANNOYING time limit appeared on the clipboard. I have no idea if it was intentional on Apple's part, and if so I have no idea what possible benevolent purpose it could serve, but I certainly don't like it.

I hope someone out there can shed some light on this. For example, is everyone with iOS 12.x experiencing this? Or are some of you still able to paste hours later? And if you are, how's your iPhone (or iPad) different than my iPhone (an old 6s)? Is it some app I have installed that copies NULL into the clipboard periodically?