So far as I know there is no resolution. I also use spotify but the audio cues still worked with wired earphones.
I found the same, occasionally start audio cues work but segments and times...never worked.
Also apple watch 5 audio cues are not synced to apple air pods.
It appears that audio cues are not synced with apple watch 5 to apple airpods. Strava needs to upgrade apple watch and airpod support.