Am I the only one that's also seeing this issue on device? I started noticing it with iOS 14 and it's continued intermittently on iOS 15 too. Every once in a while my app just stops being able to paste text that was copied from anywhere. Force-quitting the app fixes it so that the app can paste again.
I've never gathered a sysdiagnose or anything, but I do have logs from when it's happened in the simulator too.
2022-01-19 22:57:34.052240-0600 Testing[13092:3724690] [scoped] <0x283552940 file:///var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285>: internal sandbox error for <StartAccessing>
2022-01-19 22:57:34.060486-0600 Testing[13092:3724763] [claims] Upload preparation for claim 2B831962-7238-4C74-B05E-396F22C916EA completed with error: Error Domain=NSCocoaErrorDomain Code=257 "The file “e773525714f94678cc813686e707bb53ec1d2285” couldn’t be opened because you don’t have permission to view it." UserInfo={NSURL=file:///var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285, NSFilePath=/var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285, NSUnderlyingError=0x281ddb0f0 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}
2022-01-19 22:57:36.086917-0600 Testing[13092:3724763] [scoped] sandbox_extension_consume error=[12: Cannot allocate memory] for path /var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285
2022-01-19 22:57:36.087037-0600 Testing[13092:3724763] [scoped] <0x28354b600 file:///var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285>: internal sandbox error for <StartAccessing>
2022-01-19 22:57:36.094329-0600 Testing[13092:3724690] [claims] Upload preparation for claim 1B54B832-0C50-4ABE-A4CA-72331726C2D5 completed with error: Error Domain=NSCocoaErrorDomain Code=257 "The file “e773525714f94678cc813686e707bb53ec1d2285” couldn’t be opened because you don’t have permission to view it." UserInfo={NSURL=file:///var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285, NSFilePath=/var/mobile/Library/Caches/com.apple.Pasteboard/eb77e5f8f043896faf63b5041f0fbd121db984dd/e773525714f94678cc813686e707bb53ec1d2285, NSUnderlyingError=0x281dcdbf0 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}