Ok. I may have found a fix for this that others may be able to make use of. Thanks to @jadardev as your comment above gave me the seed of what I needed. The font I was working with was Font Awesome, and I was loading it like this: label.font = [UIFont fontWithName:@"Font Awesome 6 Pro Regular" size:17]; I got this font name by inspecting the file, and it was working just fine except for intermittently failing linked to low memory as other posters have observed. Having spotted this I starting experimenting and noticed using UIFont.fontNames(forFamilyName:_) that actually this font was described differently as FontAwesome6Pro-Regular. I switched to referring to the font by that name and weirdly, that doesn't seem to experience the problem. You could argue that i'd been using the wrong font name the whole time, but surely then it would never have worked. In any case, i'm happy because this now seems to work and hope this solution helps others.

I also have this problem, but can trigger the issue to occur reliably by using the iOS Simulator "Simulate Memory Warning" function. This would seem to suggest that when the device is memory constrained it unloads fonts from memory, but then doesn't do a good job of reloading them again when they're needed. Getting this today using the latest Xcode 15.2