Be sure the 3.5 mm plug has been fully inserted into the line-in port on the Five. You might also try changing the Audio Compression setting to Compressed or Automatic in the Sonos app and adjusting the Audio Delay setting under the Line-In settings of the Five to see if it makes any difference.

Thank you for your reply.
But I tried everything you wrote and it didn't change.

What model turntable do you have? Have you tried connecting the turntable to the line-in port on the other Five?

Is it repeatable: does it happen every time with the same track? Might it be a wifi issue? Maybe send Sonos a Diagnostics report after it’s happened, and then contact Support?

Thanks for the advice.
When I input the line to the other speaker, I can hear the sound from both speakers!

Thanks for the reply. I'll consider contacting support if I run into problems again.

When I played a specific record, there was no sound from one of the speakers again. Is this a problem with the record?

Has this worked fine in the past and suddenly had a problem, or have you just started using the turntable?

Does the cord have a stereo 3.5mm jack?

Thank you for your reply.It has a stereo 3.5mm jack.When I bought a record, suddenly one of the Fives stopped producing sound. I got the same symptom when I played another record.I replaced the speakers connected to the turntable and it was fixed, but when I played the record that had the problem, I could only hear one again.

The fact that it happens with either speaker suggests to me that there is no hardware fault with the line-in ports on the Fives.  Is it just this record?  Do other records play fine through both speakers?  Do other sources play fine (e.g. radio)?

I can’t help wondering if it is the cord/connector that has an intermittent issue, but that depends a bit on your answers to my questions.

Thank you for your reply.
It's a little complicated problem. Other records can be heard from both speakers. When I play a particular record, I can only hear it from one speaker, and then the other records can only be heard from one speaker. Occasionally, both speakers will sound, but most will only sound from one speaker. Other than vinyl records, such as Apple Music, can be heard from both speakers.

I think I would try another cable before you spend too much more time trying to fix this. 

Do you have any other device{s} you could play through the line in, for example a phone?

Is it always the same speaker that won’t play? Let’s call them A and B, and A is the left channel of your stereo pair. When you plug the turntable into speaker A, which doesn’t play? When you plug into B, which doesn’t play? Now reconfigure them so A is the right channel. Which now won’t play when plugged alternately into A and B?

Thank you for your reply.
I think the cable is fine. I checked the cable using the phone and tried another cable.

When I connect the speaker to the phone with a cable, the sound comes from only one speaker.

Thanks for the reply.

The speaker on the one I'm connecting the turntable to does make a sound. The speakers without the turntable are not sounding.

I took your advice and switched the left and right speakers, and now I get sound from both speakers. However, when I played a particular song from a particular record, the sound only came out of the speaker that was connected to the cable.

I think the problem is with the record.