Given comment 15 this problem looks similar to bug 1695591 which is caused by overly large widgets (for example a tooltip that contains a very long string and does not attempt to truncate it.
Bug 1746812 Comment 17 Edit History
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Given comment 15 this problem looks similar to bug 1695591 which is caused by overly large widgets (for example a tooltip that contains a very long string and does not attempt to truncate it).