Windows 7 + Firefox 78.0.2 + Web Clipper 7.12.5
Debian bullseye + 78.0.2 + Web Clipper 7.12.5
Neither could save a bookmark of GitLab.com https://gitlab.com/gitlab-org, or my own GitLab instance.
It blocks infinitely with a spinning cycle with "Saving your clip...".
However, Chrome 84.0.4147.89 + Web Clipper 7.12.8 works in both of Windows 7 and Debian bullseye.
BTW, why the version of Web Clipper in Firefox ADD-ONS (7.12.5 updated at 2020/4/14) differs from that in Chrome web store (7.12.8 updated at 2020/7/8) ?