This is happening due to a change on the bedrock attribution service side, which is currently dropping attribution if `utm_content` is set. This should be resolved soon.
Bug 1538106 Comment 6 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
This is happening due to a change on the bedrock attribution service side, which is currently (erroneously) not propagating utm parameters (resulting in no attribution) if `utm_content` is set at all. This should be resolved soon.