Playback time: currentTime() not changing

A user is having an issue with the playback time not changing. Related: 4576716-zd-woothemes

### Additional information

In `PlaybackManager` currentTime is determined like so:

```
func currentTime() -> TimeInterval {
guard let episode = currentEpisode() else { return -1 }

if seekingTo >= 0, seekingTo <= duration(), !playing() { return seekingTo }

let playerTime = !aboutToPlay.value ? player?.currentTime() ?? 0 : 0

if playerTime <= 0 {
let startFromTime = startFromTimeForCurrentEpisode()
return episode.playedUpTo < 1 ? startFromTime : episode.playedUpTo
}

return playerTime
}
```

In the report is informed that this time gets "stuck", you can see it in their logs:

```
2021-12-07 10:10:58 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:10:59 Sent position 1 status 2 for episode Consider the lobstermen to server
2021-12-07 10:11:30 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:12:02 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:12:34 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:13:06 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:13:06 Sent position 1 status 2 for episode Consider the lobstermen to server
2021-12-07 10:13:38 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:14:10 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:14:42 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:15:14 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:15:14 Sent position 1 status 2 for episode Consider the lobstermen to server
2021-12-07 10:15:46 saving played up to 1.38 for episode Consider the lobstermen
2021-12-07 10:16:18 saving played up to 1.38 for episode Consider the lobstermen
```

I can see this happening in the code above if the `seekingTo` time is still set or `aboutToPlay` both of which might be subject to either race conditions or a path we haven't coded for.

Start at PlaybackManager.currentTime(), then trace the seekingTo, aboutToPlay, player.currentTime(), and playedUpTo states against the supplied logs. Reproduce the stuck playback-time report and determine which state remains active; done means currentTime() advances during playback and the logged saved positions increase normally.

Written by the indexing model from the issue text.