Hey Daniel, welcome to the community and thanks for your comprehensive description of the issue! It seems like both reports (jest and cypress) show 100% coverage for that line/condition, so probably the discrepancy is introduced by SonarQube when merging the lcov reports.
A similar issue was reported not long ago, and it was fixed in SonarJS 12.1, which is bundled with SonarQube 2026.2 onwards. Before flagging this for our developers, could you please try analyzing it on SonarQube 2026.2? If you have a testing instance, then you could try upgrading it and running the analysis against it. If the issue persists, I’ll be happy to ask devs to take a look.