I have a promotion with downstream job and manual conditions:

						conditions {
							manual 'acme'
                                                        downstream(false, 'acme-Release-DSL')
						}

It has been working correctly for some time.
Today after giving the manual approval the promotion failed to start.
The page showed

This promotion has not happened.
Met Qualification

Pressing re-execute promotion opens URL JobName/177/PromotionName/build with a 404 status.

There are no relevant entries in Jenkins log.
Job folder on Jenkins master looks OK, the PromotionName folder with logs etc. is there.

I was only able to execute the promotion by using "Force Promotion". When it executed it got the number immediately following last promotion – it's not a case of promotion being temporarily invisible as in JENKINS-39648