Clipboard issues seem to affect only some users and in different ways, see tdf#62196. Potentially fixed by tdf#140813 resolved in 7.1.3 version according to bug report. If you are happy to try out Latest version it might be worth it for you.
Do you have a clipboard manager? Try turning it off and seeing if that helps.
Try copying using a different method e.g. Ctrl+C instead of clicking icon or menu; or clicking icon instead…
Try copying twice.