Were you also using Electrum portable for Bitcoin, or was that working because it was the full version?
And is it possible for you to provide a TX which reproduces this error so that it can go into an Issue on the Github? (Not your original, TX, of course, because of privacy concerns.)
(Ideally, you would open the Issue in Github with all the supporting details, but if you at least provide the necessary info here to reproduce the error, someone else can open the Issue. Either way, the Issue is the way to get the problem eventually fixed.)