Jordi, since you have a way to reproduce the issue, could you try this version https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/GVD85O40TOSRlN1kyRYM8w/runs/0/artifacts/public/build/target.tar.bz2 which includes a fix for the -2-and-below case?
Bug 1606721 Comment 14 Edit History
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Jordi, since you have a way to reproduce the issue, could you try this version https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/GVD85O40TOSRlN1kyRYM8w/runs/0/artifacts/public/build/target.tar.bz2 (from the 'try' build https://treeherder.mozilla.org/#/jobs?repo=try&revision=aae490c8c171fb9090acbe9642c83322a35ebffe&selectedJob=297252022) which includes a fix for the -2-and-below case?