I didn't encounter this issue, but from what I've read here and there, you should:
* make sure you are working with SegWit addresses, else it won't work -> see https://github.com/spesmilo/electrum/issues/3302#issuecomment-379303347
* make sure you run Electrum with --offline flag -> see https://www.reddit.com/r/Electrum/comments/ciieft/issue_with_offline_signing/

I didn't find anybody telling that they've solved this issue by doing this, so I don't know more...